Crystals

9 pages, 3470 KiB

Open AccessEditor’s ChoiceArticle

Controllable Liquid Crystal Micro Tube Laser

by Jia-De Lin, Po-Chen Wu, Ting-Shan Mo, Bing-Yau Huang, Chie-Tong Kuo and Chia-Rong Lee

Crystals 2021, 11(12), 1510; https://doi.org/10.3390/cryst11121510 - 3 Dec 2021

Viewed by 2570

This study demonstrates controllable random lasing emissions in a dye-doped nematic liquid crystal (DDNLC)-infiltrated microcapillary. The emission wavelength of the micro tube laser can be adjusted by changing the focusing position of the pumped pulses on the center or the periphery of the [...] Read more.

This study demonstrates controllable random lasing emissions in a dye-doped nematic liquid crystal (DDNLC)-infiltrated microcapillary. The emission wavelength of the micro tube laser can be adjusted by changing the focusing position of the pumped pulses on the center or the periphery of the liquid crystal region of the microcapillary. In addition, with doping azo-dyes in the DDNLC of the micro tube laser, optical controllability of the lasing intensity and wavelength can be further achieved. The controllable micro tube laser may find highly widespread photonic applications in multicolor emitting sources, and vibration and UV sensors. Full article

(This article belongs to the Special Issue Liquid Crystal Composites)

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7 pages, 1815 KiB

Open AccessEditor’s ChoiceArticle

As-Grown Domain Structure in Calcium Orthovanadate Crystals

by Ekaterina Shishkina, Vladimir Yuzhakov, Maksim Nebogatikov, Elena Pelegova, Eduard Linker, Lyudmila Ivleva and Vladimir Shur

Crystals 2021, 11(12), 1508; https://doi.org/10.3390/cryst11121508 - 3 Dec 2021

Cited by 4 | Viewed by 1774

Abstract

An as-grown domain structure in nominally pure and Mn-doped calcium orthovanadate (CVO) crystals was studied by several methods of domain imaging: optical microscopy, piezoelectric force microscopy, and Cherenkov-type second harmonic generation. The combination of imaging methods provided an opportunity for comprehensive study of [...] Read more.

An as-grown domain structure in nominally pure and Mn-doped calcium orthovanadate (CVO) crystals was studied by several methods of domain imaging: optical microscopy, piezoelectric force microscopy, and Cherenkov-type second harmonic generation. The combination of imaging methods provided an opportunity for comprehensive study of the domain structure on the polar surface and in the bulk of the samples. It was shown that, in nominally pure CVO crystals, an irregular 3D maze of rounded domains, with charged walls, essentially tilted from the polar direction, was present. It was proposed that the domain structure was formed just below the phase transition temperature and persisted during subsequent cooling. Such behavior is due to effective bulk screening of the depolarization field and a low value of the pyroelectric field which appears during cooling. The revealed formation of triangular domains and flat fragments of domain walls in Mn-doped CVO was attributed to polarization reversal under the action of the polar component of the pyroelectric field, above the threshold value for domain switching. This fact represents the first observation of the domain switching in CVO crystals. Full article

(This article belongs to the Special Issue Crystal Nucleation and Growth Kinetics)

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11 pages, 5841 KiB

Open AccessEditor’s ChoiceArticle

Linking Time-Domain Vibration Behaviors to Spatial-Domain Propagating Waves in a Leaf-like Gradient-Index Phononic Crystal Lens

by Kuo-Chih Chuang, Dan-Feng Wang, Jun-Jie Liu and Chan-Yi Liao

Crystals 2021, 11(12), 1490; https://doi.org/10.3390/cryst11121490 - 1 Dec 2021

Cited by 1 | Viewed by 1900

Abstract

It is known that a propagating wave at a certain spatial point can be decomposed into plane waves propagating at different angles. In this work, by designing a gradient index phononic crystal lens (GRIN PCL) with transverse-continuous leaf-like unit cells, we theoretically and [...] Read more.

It is known that a propagating wave at a certain spatial point can be decomposed into plane waves propagating at different angles. In this work, by designing a gradient index phononic crystal lens (GRIN PCL) with transverse-continuous leaf-like unit cells, we theoretically and experimentally show that the spatial-domain propagating waves in finite periodic structures can be linked to their time-domain vibration behaviors. The full-field instantaneous focusing behaviors of Lamb waves in the proposed leaf-like GRIN PCL give an example of the wave-vibration linkage in finite periodic structures while allowing a certain complexity. The conclusion in this paper can help one skip iterative time-consuming finite element analysis (e.g., time-stepping solutions) to avoid possible numerical instabilities occurred in calculating transient wave field on practical finite metamaterials or phononic crystals having unit cells with complicated configurations. Full article

(This article belongs to the Special Issue Recent Advances in Phononic Crystals and Acoustic Metamaterials)

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14 pages, 5827 KiB

Open AccessEditor’s ChoiceArticle

An Experimental and Theoretical Study on the Effect of Silver Nanoparticles Concentration on the Structural, Morphological, Optical, and Electronic Properties of TiO₂ Nanocrystals

by Faheem Ahmed, Mohammed Benali Kanoun, Chawki Awada, Christian Jonin and Pierre-Francois Brevet

Crystals 2021, 11(12), 1488; https://doi.org/10.3390/cryst11121488 - 30 Nov 2021

Cited by 27 | Viewed by 3556

Abstract

In this work, pure and silver (Ag)-loaded TiO₂ nanocrystals (NCs) with various concentrations of Ag were prepared by soft chemical route and the effect of Ag nanoparticles (NPs) on the functional properties of TiO₂ was studied. X-ray diffraction (XRD) and Raman [...] Read more.

In this work, pure and silver (Ag)-loaded TiO₂ nanocrystals (NCs) with various concentrations of Ag were prepared by soft chemical route and the effect of Ag nanoparticles (NPs) on the functional properties of TiO₂ was studied. X-ray diffraction (XRD) and Raman studies confirmed that the synthesized product had single-phase nature and high crystalline quality. The crystallite size was decreased from 18.3 nm to 13.9 nm with the increasing in concentration of Ag in TiO₂ NCs. FESEM micrographs showed that the pure and AgNPs-loaded TiO₂ have spherical morphology and uniform size distribution with the size ranging from 20 to 10 nm. Raman spectroscopy performed on pure and AgNPs-loaded TiO₂ confirms the presence of anatase phase and AgNPs. Optical properties show the characteristics peaks of TiO₂ and the shifting of the peaks position was observed by changing the concentration of Ag. The tuning of bandgap was found to be observed with the increase in Ag, which could be ascribed to the synergistic effect between silver and TiO₂ NCs. Density functional theory calculations are carried out for different Ag series of doped TiO₂ lattices to simulate the structural and electronic properties. The analysis of the electronic structures show that Ag loading induces new localized gap states around the Fermi level. Moreover, the introduction of dopant states in the gap region owing to Ag doping can be convenient to shift the absorption edge of pristine TiO₂ through visible light. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 6765 KiB

Open AccessEditor’s ChoiceArticle

Influence of Crystal Plasticity Parameters on the Strain Hardening Behavior of Polycrystals

by Mahdieh Shahmardani, Napat Vajragupta and Alexander Hartmaier

Crystals 2021, 11(12), 1473; https://doi.org/10.3390/cryst11121473 - 27 Nov 2021

Cited by 3 | Viewed by 2665

Abstract

The effective mechanical properties of a polycrystal depend directly on the single-crystal properties of each grain and its crystallographic orientation with respect to the load axis. While the micromechanical approach has been used quite extensively to study the influence of grain shape and [...] Read more.

The effective mechanical properties of a polycrystal depend directly on the single-crystal properties of each grain and its crystallographic orientation with respect to the load axis. While the micromechanical approach has been used quite extensively to study the influence of grain shape and crystallographic texture on the resulting mechanical behavior of a polycrystal, the influence of the crystal plasticity parameters, which describe the constitutive behavior of the single crystal, requires to be investigated systemically because, typically, these parameters are fitted to describe a given material behavior. In the current research, this gap is filled by systemically studying the effect of changes in crystal plasticity parameters on the effective mechanical properties of polycrystals. The numerical model employed here consists of a representative volume element of 100 grains, and the material properties are described by using a non-local crystal plasticity model. A proper homogenization technique was used to homogenize the micromechanical results to an effective macroscopic material response. The equivalent stress versus equivalent plastic strain curve was obtained numerically by introducing the Voce-type hardening law, mimicking the material behavior in uniaxial tensile tests. The four parameters of the Voce-type hardening law were fitted to the macroscopic stress-strain curves, and the correlation between the crystal plasticity parameters and the Voce parameters has been studied, which is an efficient way to study the influence of microscopic material descriptions on the macroscopic behavior of polycrystals. Full article

(This article belongs to the Special Issue Micromechanical Modelling and Its Applications to Polycrystals)

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19 pages, 4571 KiB

Open AccessEditor’s ChoiceArticle

The Principle of Maximal Simplicity for Modular Inorganic Crystal Structures

by Sergey V. Krivovichev

Crystals 2021, 11(12), 1472; https://doi.org/10.3390/cryst11121472 - 26 Nov 2021

Cited by 4 | Viewed by 2225

Abstract

Modularity is an important construction principle of many inorganic crystal structures that has been used for the analysis of structural relations, classification, structure description and structure prediction. The principle of maximal simplicity for modular inorganic crystal structures can be formulated as follows: in [...] Read more.

Modularity is an important construction principle of many inorganic crystal structures that has been used for the analysis of structural relations, classification, structure description and structure prediction. The principle of maximal simplicity for modular inorganic crystal structures can be formulated as follows: in a modular series of inorganic crystal structures, the most common and abundant in nature and experiments are those arrangements that possess maximal simplicity and minimal structural information. The latter can be quantitatively estimated using information-based structural complexity parameters. The principle is applied for the modular series based upon 0D (lovozerite family), 1D (biopyriboles) and 2D (spinelloids and kurchatovite family) modules. This principle is empirical and is valid for those cases only, where there are no factors that may lead to the destabilization of simplest structural arrangements. The physical basis of the principle is in the relations between structural complexity and configurational entropy sensu stricto (which should be distinguished from the entropy of mixing). It can also be seen as an analogy of the principle of least action in physics. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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14 pages, 1098 KiB

Open AccessEditor’s ChoicePerspective

Perspective/Discussion on “Quantum Mechanical Metric for Internal Cohesion in Cement Crystals” by C. C. Dharmawardhana, A. Misra and Wai-Yim Ching

by Natt Makul

Crystals 2021, 11(12), 1450; https://doi.org/10.3390/cryst11121450 - 24 Nov 2021

Viewed by 1918

Abstract

The single most important structural material, and the major Portland cement binding phase in application globally, is calcium silicate hydrate (C-S-H). The concentration has increasingly changed due to its atomic level comprehension because of the chemistry and complex structures of internal C-S-H cohesion [...] Read more.

The single most important structural material, and the major Portland cement binding phase in application globally, is calcium silicate hydrate (C-S-H). The concentration has increasingly changed due to its atomic level comprehension because of the chemistry and complex structures of internal C-S-H cohesion in cement crystals at different lengths. This perspective aimed at describing on calcium-silicate-hydrates (C-S-H) structures with differing contents of Ca/Si ratio based on the report entitled “Quantum mechanical metric for internal cohesion in cement crystals” published by C. C. Dharmawardhana, A. Misra and Wai-Yim Ching. Crystal structural and bond behaviors in synthesized C-S-H were also discussed. The investigator studied large subset electronic structures and bonding of the common C-S-H minerals. From each bonding type, the results and findings show a wide variety of contributions, particularly hydrogen bonding, that allow critical analyses of spectroscopic measurement and constructions of practical C-S-H models. The investigator found that the perfect overall measurement for examining crystal cohesions of the complex substances is the total bond density (TBOD), which needs to be substituted for traditional metrics such as calcium to silicon ratios. In comparison to Tobermorite and Jennite, hardly known orthorhombic phased Suolunites were revealed to have greater cohesion and total order distribution density than those of the hydrated Portland cement backbone. The findings of the perspective showed that utilizing quantum mechanical metrics, the total bond orders and total bond order distributions are the most vital criteria for assessing the crystalline cohesions in C-S-H crystals. These metrics encompass effects of both interatomic interactions and geometric elements. Thus, the total bond order distribution and bond order offer comprehensive and in-depth measures for the overall behaviors of these diverse groups of substances. The total bond order distributions must clearly be substituted for the conventional and longstanding Ca/Si ratios applied in categorizing the cement substances. The inconspicuous Suolunite crystals were found to have the greatest total bond order distributions and the perfect bonding characteristics, compositions, and structures for cement hydrates. Full article

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9 pages, 1953 KiB

Open AccessEditor’s ChoiceArticle

AlGaN-Based 1.55 µm Phototransistor as a Crucial Building Block for Optical Computers

by Daniel Hofstetter, Cynthia Aku-Leh, Hans Beck and David P. Bour

Crystals 2021, 11(11), 1431; https://doi.org/10.3390/cryst11111431 - 22 Nov 2021

Cited by 2 | Viewed by 2306

Abstract

An optically activated, enhancement mode heterostructure field effect transistor is proposed and analytically studied. A particular feature of this device is its gate region, which is made of a photovoltaic GaN/AlN-based superlattice detector for a wavelength of 1.55 µm. Since the inter-subband transition [...] Read more.

An optically activated, enhancement mode heterostructure field effect transistor is proposed and analytically studied. A particular feature of this device is its gate region, which is made of a photovoltaic GaN/AlN-based superlattice detector for a wavelength of 1.55 µm. Since the inter-subband transition in this superlattice does normally not interact with TE-polarized (or vertically incoming) radiation, a metallic second-order diffraction grating on the transistor gate results in a re-orientation of the light into the horizontal direction—thus providing the desired TM-polarization. Upon illumination of this gate, efficient inter-subband absorption lifts electrons from the ground to the first excited quantized state. Due to partial screening of the strong internal polarization fields between GaN quantum wells and AlN barriers, this slightly diagonal transition generates an optical rectification voltage. Added to a constant electrical bias, this optically produced gate voltage leads to a noticeable increase of the transistor’s source-drain current. The magnitude of the bias voltage is chosen to result in maximal transconductance. Since such a phototransistor based on high-bandgap material is a device involving only fast majority carriers, very low dark and leakage currents are expected. The most important advantage of such a device, however, is the expected switching speed and, hence, its predicted use as an optical logic gate for photonic computing. In the absence of a p-n-junction and thus of both a carrier-induced space charge region, and the parasitic capacitances resulting thereof, operation frequencies of appropriately designed, sufficiently small phototransistors reaching 100 GHz are envisaged. Full article

(This article belongs to the Special Issue Advances in GaN-Based Optoelectronic Materials and Devices)

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11 pages, 1358 KiB

Open AccessEditor’s ChoiceArticle

Statistical Theory of Helical Twisting in Nematic Liquid Crystals Doped with Chiral Nanoparticles

by Mikhail A. Osipov, Alexey S. Merekalov and Alexander A. Ezhov

Crystals 2021, 11(11), 1432; https://doi.org/10.3390/cryst11111432 - 22 Nov 2021

Viewed by 2361

Abstract

A molecular field theory of the cholesteric ordering in nematic nanocomposites doped with chiral nanoparticles was developed taking into consideration chiral dispersion interaction between rod-like nanoparticles. It was shown that the inverse pitch of the cholesteric helical structure is proportional to the anisotropy [...] Read more.

A molecular field theory of the cholesteric ordering in nematic nanocomposites doped with chiral nanoparticles was developed taking into consideration chiral dispersion interaction between rod-like nanoparticles. It was shown that the inverse pitch of the cholesteric helical structure is proportional to the anisotropy of the effective polarizability and the anisotropy of the effective gyration tensor of a nanoparticle in the nematic host. The theory enables one to predict the helical sense inversion induced by a change of the low-frequency dielectric susceptibility of the nematic host phase. The components of the high-frequency effective polarizability and the effective optical activity of a gold rod-like nanoparticle in a particular nematic solvent were calculated numerically. Full article

(This article belongs to the Special Issue Selected Papers from the 2nd International Online Conference on Crystals)

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14 pages, 2628 KiB

Open AccessEditor’s ChoiceArticle

The Crystal Structure of Nα-p-tosyl-lysyl Chloromethylketone-Bound Oligopeptidase B from Serratia Proteamaculans Revealed a New Type of Inhibitor Binding

by Vladimir I. Timofeev, Dmitry E. Petrenko, Yulia K. Agapova, Anna V. Vlaskina, David M. Karlinsky, Anna G. Mikhailova, Inna P. Kuranova and Tatiana V. Rakitina

Crystals 2021, 11(11), 1438; https://doi.org/10.3390/cryst11111438 - 22 Nov 2021

Cited by 4 | Viewed by 2188

Abstract

A covalent serine protease inhibitor—Na-p-Tosyl-Lysyl Chloromethylketone (TCK) is a modified lysine residue tosylated at the N-terminus and chloromethylated at the C-terminus, one molecule of which is capable of forming two covalent bonds with both Ser and His catalytic residues, was co-crystallized with modified [...] Read more.

A covalent serine protease inhibitor—Na-p-Tosyl-Lysyl Chloromethylketone (TCK) is a modified lysine residue tosylated at the N-terminus and chloromethylated at the C-terminus, one molecule of which is capable of forming two covalent bonds with both Ser and His catalytic residues, was co-crystallized with modified oligopeptidase B (OpB) from Serratia proteomaculans (PSPmod). The kinetics study, which preceded crystallization, shows that the stoichiometry of TCK-dependent inhibition of PSPmod was 1:2 (protein:inhibitor). The crystal structure of the PSPmod-TCK complex, solved at a resolution of 2.3 Å, confirmed a new type of inhibitor binding. Two TCK molecules were bound to one enzyme molecule: one with the catalytic Ser, the other with the catalytic His. Due to this mode of binding, the intermediate state of PSPmod and the disturbed conformation of the catalytic triad were preserved in the PSPmod-TCK complex. Nevertheless, the analysis of the amino acid surroundings of the inhibitor molecule bound to the catalytic Ser and its comparison with that of antipain-bound OpB from Trypanosoma brucei provided an insight in the structure of the PSPmod substrate-binding pocket. Supposedly, the new type of binding is typical for the interaction of chloromethylketone derivatives with two-domain OpBs. In the open conformational state that these enzymes are assumed in solution, the disordered configuration of the catalytic triad prevents simultaneous interaction of one inhibitor molecule with two catalytic residues. Full article

(This article belongs to the Section Biomolecular Crystals)

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11 pages, 3169 KiB

Open AccessEditor’s ChoiceArticle

Characterization of Structural Defects in (Cd,Zn)Te Crystals Grown by the Travelling Heater Method

by Jiaona Zou, Alex Fauler, Alexander S. Senchenkov, Nikolai N. Kolesnikov, Lutz Kirste, Merve Pinar. Kabukcuoglu, Elias Hamann, Angelica Cecilia and Michael Fiederle

Crystals 2021, 11(11), 1402; https://doi.org/10.3390/cryst11111402 - 18 Nov 2021

Cited by 4 | Viewed by 2550

Abstract

Structural defects and compositional uniformity remain the major problems affecting the performance of (Cd, Zn)Te (CZT) based detector devices. Understanding the mechanism of growth and defect formation is therefore fundamental to improving the crystal quality. In this frame, space experiments for the growth [...] Read more.

Structural defects and compositional uniformity remain the major problems affecting the performance of (Cd, Zn)Te (CZT) based detector devices. Understanding the mechanism of growth and defect formation is therefore fundamental to improving the crystal quality. In this frame, space experiments for the growth of CZT by the Travelling Heater Method (THM) under microgravity are scheduled. A detailed ground-based program was performed to determine experimental parameters and three CZT crystals were grown by the THM. The structural defects, compositional homogeneity and resistivity of these ground-based crystals were investigated. A ZnTe content variation was observed at the growth interface and a high degree of stress associated with extensive dislocation networks was induced, which propagated into the grown crystal region according to the birefringence and X-ray White Beam Topography (XWBT) results. By adjusting the growth parameters, the ZnTe variations and the resulting stress were efficiently reduced. In addition, it was revealed that large inclusions and grain boundaries can generate a high degree of stress, leading to the formation of dislocation slip bands and subgrain boundaries. The dominant defects, including grain boundaries, dislocation networks and cracks in the interior of crystals, led to the resistivity variation in the crystals. The bulk resistivity of the as-grown crystals ranged from 10⁹ Ωcm to 10¹⁰ Ωcm. Full article

(This article belongs to the Special Issue Research about Vital Organic Chelates and Metal Ion Complexes)

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10 pages, 2420 KiB

Open AccessEditor’s ChoiceArticle

Determination of Absolute Structure of Chiral Crystals Using Three-Wave X-ray Diffraction

by Ksenia Kozlovskaya, Elena Ovchinnikova, Jun Kokubun, Andrei Rogalev, Fabrice Wilhelm, Francois Guillou, Francois de Bergevin, Alisa F. Konstantinova and Vladimir E. Dmitrienko

Crystals 2021, 11(11), 1389; https://doi.org/10.3390/cryst11111389 - 15 Nov 2021

Cited by 4 | Viewed by 3083

Abstract

We propose a new method to determine the absolute structure of chiral crystals, which is based on the chiral asymmetry of multiple scattering diffraction. It manifests as a difference in the azimuthal dependence of the forbidden Bragg reflection intensity measured with left and [...] Read more.

We propose a new method to determine the absolute structure of chiral crystals, which is based on the chiral asymmetry of multiple scattering diffraction. It manifests as a difference in the azimuthal dependence of the forbidden Bragg reflection intensity measured with left and right circularly polarized X-ray beams. Contrary to the existing ones, the suggested method does not use X-ray anomalous dispersion. The difference between the Renninger scans with circularly polarized X-rays has been experimentally demonstrated for the 001 reflection intensities in the right- and left-handed quartz single crystals. A Jmulti-based code on model-independent three-wave-diffraction approach has been developed for quantitative description of our experimental results. The proposed method can be applied to various structures including opaque, organic and monoatomic crystals, even with only light elements. To determine the type of isomer, the Renninger plot of a single forbidden reflection is sufficient. Full article

(This article belongs to the Special Issue Synchrotron-Based X-Ray Techniques for the Study of New Crystalline Materials)

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19 pages, 1077 KiB

Open AccessEditor’s ChoiceArticle

Some Issues on Crystal Plasticity Models Formulation: Motion Decomposition and Constitutive Law Variants

by Peter Trusov, Alexey Shveykin and Nikita Kondratev

Crystals 2021, 11(11), 1392; https://doi.org/10.3390/cryst11111392 - 15 Nov 2021

Cited by 10 | Viewed by 2587

Abstract

In this paper, kinematic relations and constitutive laws in crystal plasticity are analyzed in the context of geometric nonlinearity description and fulfillment of thermodynamic requirements in the case of elastic deformation. We consider the most popular relations: in finite form, written in terms [...] Read more.

In this paper, kinematic relations and constitutive laws in crystal plasticity are analyzed in the context of geometric nonlinearity description and fulfillment of thermodynamic requirements in the case of elastic deformation. We consider the most popular relations: in finite form, written in terms of the unloaded configuration, and in rate form, written in terms of the current configuration. The presence of a corotational derivative in the relations formulated in terms of the current configuration testifies to the fact that the model is based on the decomposition of motion into the deformation motion and the rigid motion of a moving coordinate system, and precisely the stress rate with respect to this coordinate system is associated with the strain rate. We also examine the relations of the mesolevel model with an explicit separation of a moving coordinate system and the elastic distortion of crystallites relative to it in the deformation gradient. These relations are compared with the above formulations, which makes it possible to determine how close they are. The results of the performed analytical calculations show the equivalence or similarity (in the sense of the response determined under the same influences) of the formulation and are supported by the results of numerical calculation. It is shown that the formulation based on the decomposition of motion with an explicit separation of the moving coordinate system motion provides a theoretical framework for the transition to a similar formulation in rate form written in terms of the current configuration. The formulation of this kind is preferable for the numerical solution of boundary value problems (in a case when the current configuration and, consequently, contact boundaries, are not known a priori) used to model the technological treatment processes. Full article

(This article belongs to the Special Issue Crystal Plasticity (Volume II))

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19 pages, 4026 KiB

Open AccessEditor’s ChoiceArticle

Strain-Gradient Crystal Plasticity Finite Element Modeling of Slip Band Formation in α-Zirconium

by Omid Sedaghat and Hamidreza Abdolvand

Crystals 2021, 11(11), 1382; https://doi.org/10.3390/cryst11111382 - 12 Nov 2021

Cited by 6 | Viewed by 2877

Abstract

Two methods for the determination of geometrically necessary dislocation (GND) densities are implemented in a lower-order strain-gradient crystal plasticity finite element model. The equations are implemented in user material (UMAT) subroutines. Method I has a direct and unique solution for the density of [...] Read more.

Two methods for the determination of geometrically necessary dislocation (GND) densities are implemented in a lower-order strain-gradient crystal plasticity finite element model. The equations are implemented in user material (UMAT) subroutines. Method I has a direct and unique solution for the density of GNDs, while Method II has unlimited solutions, where an optimization technique is used to determine GND densities. The performance of each method for capturing the formation of slip bands based on the calculated GND maps is critically analyzed. First, the model parameters are identified using single crystal simulations. This is followed by importing the as-measured microstructure for a deformed α-zirconium specimen into the finite element solver to compare the numerical results obtained from the models to those measured experimentally using the high angular resolution electron backscatter diffraction technique. It is shown that both methods are capable of modeling the formation of slip bands that are parallel to those observed experimentally. Formation of such bands is observed in both GND maps and plastic shear strain maps without pre-determining the slip band domain. Further, there is a negligible difference between the calculated grain-scale stresses and elastic lattice rotations from the two methods, where the modeling results are close to the measured ones. However, the magnitudes and distributions of calculated GND densities from the two methods are very different. Full article

(This article belongs to the Special Issue Crystal Plasticity (Volume II))

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11 pages, 3379 KiB

Open AccessEditor’s ChoiceArticle

Crystal Structures, Thermal and Luminescent Properties of Gadolinium(III) Trans-1,4-cyclohexanedicarboxylate Metal-Organic Frameworks

by Pavel A. Demakov, Alena A. Vasileva, Vladimir A. Lazarenko, Alexey A. Ryadun and Vladimir P. Fedin

Crystals 2021, 11(11), 1375; https://doi.org/10.3390/cryst11111375 - 11 Nov 2021

Cited by 10 | Viewed by 2906

Abstract

Four new gadolinium(III) metal-organic frameworks containing 2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen) chelate ligands and trans-1,4-cyclohexanedicarboxylate (chdc²⁻) were synthesized. Their crystal structures were determined by single-crystal X-ray diffraction analysis. All four coordination frameworks are based on the binuclear carboxylate building units. [...] Read more.

Four new gadolinium(III) metal-organic frameworks containing 2,2′-bipyridyl (bpy) or 1,10-phenanthroline (phen) chelate ligands and trans-1,4-cyclohexanedicarboxylate (chdc²⁻) were synthesized. Their crystal structures were determined by single-crystal X-ray diffraction analysis. All four coordination frameworks are based on the binuclear carboxylate building units. In the compounds [Gd₂(bpy)₂(chdc)₃]·H₂O (1) and [Gd₂(phen)₂(chdc)₃]·0.5DMF (2), the six-connected {Ln₂(L)₂(OOCR)₆} blocks form a 3D network with the primitive cubic (pcu) topology. In the compounds [Gd₂(NO₃)₂(phen)₂(chdc)₂]·2DMF (3) and [Gd₂Cl₂(phen)₂(chdc)₂]·0.3DMF·2.2dioxane (4), the four-connected {Ln₂(L)₂(X)₂OOCR)₄} units (where X = NO₃⁻ for 3 or Cl⁻ for 4) form a 2D square-grid (sql) network. The solid-state luminescent properties were investigated for the synthesized frameworks. Bpy-containing compound 1 shows no luminescence, possibly due to the paramagnetic quenching by Gd³⁺ cation. In contrast, the phenathroline-containing MOFs 2–4 possess yellow emission under visible excitation (λ_ex = 460 nm) with the tuning of the characteristic wavelength by the coordination environment of the metal center. Full article

(This article belongs to the Special Issue Hybrid Organic-Inorganic Materials Used to Improve the Environment and Human Health)

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17 pages, 4976 KiB

Open AccessEditor’s ChoiceArticle

Porosity Distribution Simulation and Impure Inclusion Analysis of Porous Crystal Layer Formed via Polythermal Process

by Yingshuang Meng, Zhonghua Li, Xiangcun Li, Wu Xiao, Gaohong He, Xuemei Wu and Xiaobin Jiang

Crystals 2021, 11(11), 1347; https://doi.org/10.3390/cryst11111347 - 5 Nov 2021

Cited by 2 | Viewed by 2140

Abstract

In this work, we investigated the porosity distribution and separation property of the porous crystal layer formed via the polythermal process. The proposed porosity distribution model, considering both the cooling profile and the crystal settling effect, provided simulative results that met the MRI [...] Read more.

In this work, we investigated the porosity distribution and separation property of the porous crystal layer formed via the polythermal process. The proposed porosity distribution model, considering both the cooling profile and the crystal settling effect, provided simulative results that met the MRI analysis experimental results with suitable agreement. Significant porosity variation from the top to the bottom of the crystal layer (

ϕ

from 0.75 to 0.55 under rapid cooling profile) was detected. Meanwhile, the vertical supersaturation degree gradient induced by the fluid fluctuation could impact nucleation and crystal growth kinetic along with crystal particle settling. The resulting crystal layer possessed various impurity inclusion conditions. Under a moderate cooling profile (0.4 K·min⁻¹), the volume fraction of closed pores against overall pores decreased from 0.75 to 0.36. The proposed model and experimental analysis approach were demonstrated to be helpful for porosity distribution simulation and impure inclusion analysis of layer crystallization. Full article

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37 pages, 12641 KiB

Open AccessEditor’s ChoiceReview

Advances in Diffraction Studies of Light-Induced Transient Species in Molecular Crystals and Selected Complementary Techniques

by Krystyna A. Deresz, Piotr Łaski, Radosław Kamiński and Katarzyna N. Jarzembska

Crystals 2021, 11(11), 1345; https://doi.org/10.3390/cryst11111345 - 3 Nov 2021

Cited by 7 | Viewed by 3161

Abstract

The review provides a summary of the current methods of tracing photoexcitation processes and structural dynamics in the solid state, putting major emphasis on the X-ray diffraction techniques (time-resolved Laue diffraction on synchrotron sources and time-resolved serial femtosecond crystallography on X-ray free-electron lasers). [...] Read more.

The review provides a summary of the current methods of tracing photoexcitation processes and structural dynamics in the solid state, putting major emphasis on the X-ray diffraction techniques (time-resolved Laue diffraction on synchrotron sources and time-resolved serial femtosecond crystallography on X-ray free-electron lasers). The recent developments and nowadays experimental possibilities in the field are discussed along with the data processing and analysis approaches, and illustrated with some striking literature examples of the respective successful studies. Selected complementary methods, such as ultrafast electron diffraction or time-resolved X-ray absorption spectroscopy, are briefly presented. Full article

(This article belongs to the Special Issue Time-Resolved X-ray Diffraction and Scattering Techniques Applied to Dynamical Processes)

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9 pages, 3062 KiB

Open AccessEditor’s ChoiceArticle

Surface Porosity of Natural Diamond Crystals after the Catalytic Hydrogenation

by Aleksei Chepurov, Valeri Sonin, Dmitry Shcheglov, Egor Zhimulev, Sergey Sitnikov, Alexander Yelisseyev and Anatoly Chepurov

Crystals 2021, 11(11), 1341; https://doi.org/10.3390/cryst11111341 - 3 Nov 2021

Cited by 2 | Viewed by 2281

Abstract

The study of diamond surfaces is traditionally undertaken in geology and materials science. As a sample material, two natural diamond crystals of type Ia were selected, and their luminescence and nitrogen state was characterized. In order to etch the surface catalytic hydrogenation was [...] Read more.

The study of diamond surfaces is traditionally undertaken in geology and materials science. As a sample material, two natural diamond crystals of type Ia were selected, and their luminescence and nitrogen state was characterized. In order to etch the surface catalytic hydrogenation was performed using Fe particles as an etchant. Micromorphology of the surface was investigated by scanning electron and laser confocal microscopy. It was demonstrated that etching occurred perpendicular to the crystal surface, with no signs of tangential etching. The average depth of caverns did not exceed 20–25 μm with a maximal depth of 40 μm. It is concluded that catalytic hydrogenation of natural type Ia diamonds is effective to produce a porous surface that can be used in composites or as a substrate material. Additionally, the comparison of results with porous microsculptures observed on natural impact diamond crystals from the Popigai astrobleme revealed a strong resemblance. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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6 pages, 2298 KiB

Open AccessEditor’s ChoiceCommunication

Liquid Crystalline Cholesteric Reflective Layers for Colored Silicon-Based Solar Cells

by Sangwok Bae, Dong-Sun Park and Suk-Won Choi

Crystals 2021, 11(11), 1336; https://doi.org/10.3390/cryst11111336 - 1 Nov 2021

Cited by 1 | Viewed by 2548

Abstract

The performance of a prototype opaque-type colored silicon-based solar cell integrated with liquid crystalline cholesteric layers is investigated. These devices were developed using only organic components and wet processes, without complicated vacuum processes. The evaluated performances of the prototype solar cells were inferior [...] Read more.

The performance of a prototype opaque-type colored silicon-based solar cell integrated with liquid crystalline cholesteric layers is investigated. These devices were developed using only organic components and wet processes, without complicated vacuum processes. The evaluated performances of the prototype solar cells were inferior to those of the other types of previously reported colored solar cells because of the inherent limitations of the cholesteric layers, such as the limited reflectance (~50%), narrow color gamut, and viewing angle-dependent color changes. We propose effective strategies for improving the performance of colored solar cell modules integrated with cholesteric layers. Full article

(This article belongs to the Section Organic Crystalline Materials)

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20 pages, 3408 KiB

Open AccessEditor’s ChoiceReview

Liquid Crystal Thermography in Gas Turbine Heat Transfer: A Review on Measurement Techniques and Recent Investigations

by Srinath V. Ekkad and Prashant Singh

Crystals 2021, 11(11), 1332; https://doi.org/10.3390/cryst11111332 - 31 Oct 2021

Cited by 16 | Viewed by 3591

Abstract

Liquid Crystal Thermography is a widely used experimental technique in the gas turbine heat transfer community. In turbine heat transfer, determination of the convective heat transfer coefficient (h) and adiabatic film cooling effectiveness (η) is imperative in order to [...] Read more.

Liquid Crystal Thermography is a widely used experimental technique in the gas turbine heat transfer community. In turbine heat transfer, determination of the convective heat transfer coefficient (h) and adiabatic film cooling effectiveness (η) is imperative in order to design hot gas path components that can meet the modern-day engine performance and emission goals. LCT provides valuable information on the local surface temperature, which is used in different experimental methods to arrive at the local h and η. The detailed nature of h and η through LCT sets it apart from conventional thermocouple-based measurements and provides valuable insights into cooling designers for concept development and its further iterations. This article presents a comprehensive review of the state-of-the-art experimental methods employing LCT, where a critical analysis is presented for each, as well as some recent investigations (2016–present) where LCT was used. The goal of this article is to familiarize researchers with the evolving nature of LCT given the advancements in instrumentation and computing capabilities, and its relevance in turbine heat transfer problems in current times. Full article

(This article belongs to the Special Issue Liquid Crystal Thermography for Gas Turbine Heat Transfer Measurements)

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9 pages, 1755 KiB

Open AccessEditor’s ChoiceArticle

Potential of Sub-THz-Wave Generation in Li₂B₄O₇ Nonlinear Crystal at Room and Cryogenic Temperatures

by Dmitry Ezhov, Snezhana Turgeneva, Nazar Nikolaev, Alexander Mamrashev, Sergei Mikerin, Fedor Minakov, Andrey Simanchuk, Valery Antsygin, Valery Svetlichnyi, Valery Losev and Yury Andreev

Crystals 2021, 11(11), 1321; https://doi.org/10.3390/cryst11111321 - 29 Oct 2021

Cited by 3 | Viewed by 2222

Abstract

Due to their high optical damage threshold, borate crystals can be used for the efficient nonlinear down-conversion of terawatt laser radiation into the terahertz (THz) frequency range of the electromagnetic spectrum. In this work, we carried out a thorough study of the terahertz [...] Read more.

Due to their high optical damage threshold, borate crystals can be used for the efficient nonlinear down-conversion of terawatt laser radiation into the terahertz (THz) frequency range of the electromagnetic spectrum. In this work, we carried out a thorough study of the terahertz optical properties of the lithium tetraborate crystal (Li₂B₄O₇; LB4) at 295 and 77 K. Approximating the terahertz refractive index in the form of Sellmeier’s equations, we assessed the possibility of converting the radiation of widespread high-power laser sources with wavelengths of 1064 and 800 nm, as well as their second and third harmonics, into the THz range. It was found that four out of eight types of three-wave mixing processes are possible. The conditions for collinear phase matching were fulfilled only for the o − e → o type of interaction, while cooling the crystal to 77 K did not practically affect the phase-matching curves. However, a noticeable increase of birefringence in the THz range with cooling (from 0.12 to 0.16) led to an increase in the coherence length for o − o → e and e − e → e types of interaction, which are potentially attractive for the down-conversion of ultrashort laser pulses. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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14 pages, 5993 KiB

Open AccessEditor’s ChoiceArticle

Novel Device and Strategy for Growing Large, High-Quality Protein Crystals by Controlling Crystallization Conditions

by Naoki Tanigawa, Sachiko Takahashi, Bin Yan, Masayuki Kamo, Naoki Furubayashi, Koji Kubota, Koji Inaka and Hiroaki Tanaka

Crystals 2021, 11(11), 1311; https://doi.org/10.3390/cryst11111311 - 27 Oct 2021

Cited by 1 | Viewed by 2396

Abstract

Neutron diffraction experiments are informative for determining the locations of hydrogen atoms in protein molecules; however, much larger crystals are needed than those required for X-ray diffraction. Thus, additional techniques are required to grow larger crystals. Here, a unique crystallization device and strategy [...] Read more.

Neutron diffraction experiments are informative for determining the locations of hydrogen atoms in protein molecules; however, much larger crystals are needed than those required for X-ray diffraction. Thus, additional techniques are required to grow larger crystals. Here, a unique crystallization device and strategy for growing large protein crystals are introduced. The device uses two micropumps to control crystal growth by altering the precipitant concentration and regulating the pinpoint injection of dry air flow to the crystallization cell. Furthermore, the crystal growth can be observed in real time. Preliminary microbatch crystallization experiments at various concentration ranges of polyethylene glycol (PEG) 4000 and sodium chloride were first performed to elucidate optimized crystallization conditions. Based on these results, a device to precisely control the sodium chloride and PEG concentrations and the supply of dry air to the crystallization cell was used, and 1.8 mm lysozyme and 1.5 mm alpha-amylase crystals with good reproducibility were obtained. X-ray data sets of both crystals were collected at room temperature at BL2S1 of the Aichi Synchrotron Radiation Center and confirmed that these crystals were of high quality. Therefore, this crystallization device and strategy were effective for growing large, high-quality protein crystals. Full article

(This article belongs to the Special Issue Protein Crystallography: Achievements and Challenges)

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10 pages, 3711 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Crystal Structure, and Luminescent Properties of a New Holmium(III) Coordination Polymer Involving 2,5-Dihydroxy-1,4-terephthalic Acid Dianion as Ligand

by Jiaqi Li, Linan Dun, Fanming Zeng, Chun Li and Zhongmin Su

Crystals 2021, 11(11), 1294; https://doi.org/10.3390/cryst11111294 - 26 Oct 2021

Cited by 2 | Viewed by 2454

Abstract

A novel coordination polymer {[Ho₂(DHTA)₃(H2O)₅]·H₂O}n (1) was synthesized by hydrothermal synthesis (DHTA = 2,5-dihydroxy-1,4-terephthalic acid anion). The crystallographic data show that complex 1 crystallizes in a triclinic system with space group P [...] Read more.

A novel coordination polymer {[Ho₂(DHTA)₃(H2O)₅]·H₂O}n (1) was synthesized by hydrothermal synthesis (DHTA = 2,5-dihydroxy-1,4-terephthalic acid anion). The crystallographic data show that complex 1 crystallizes in a triclinic system with space group P

\bar{1}

, with a = 9.6617(17) Å, b = 11.902(2) Å, c = 13.284(2) Å, α = 100.617(3)°, β = 92.765(2)°, γ = 106.715(2)°, V = 1429.6(4) Å3, Z = 2, C₂₄H₂₄O₂₄Ho₂, and M_r = 1026.290. Complex 1 contains two eight-coordinated metal centers Ho(III). The TGA results show that the weight loss can be ascribed to the removal of the organic component from 400 to 650 °C. At the temperature above 650 °C, the residue is Holmium(III) oxide (Ho₂O₃). The luminescent results reveal that the complex has potential application as a new green luminescence material. Full article

(This article belongs to the Special Issue Self-Assembled Complexes: “Love at First Sight”)

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14 pages, 3843 KiB

Open AccessEditor’s ChoiceArticle

Photosensitive Bent-Core Liquid Crystals with Laterally Substituted Azobenzene Unit

by Diana Jágerová, Michal Šmahel, Anna Poryvai, Jan Macháček, Vladimíra Novotná and Michal Kohout

Crystals 2021, 11(10), 1265; https://doi.org/10.3390/cryst11101265 - 18 Oct 2021

Cited by 6 | Viewed by 2848

Abstract

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables [...] Read more.

Photosensitive liquid crystals represent an important class of functional materials that experience rapid development. Hereby, we present novel bent-core liquid crystals bearing a lateral substitution on the central core and in the vicinity of the photosensitive unit—an azo group. The azo group enables fast (E)-to-(Z)-isomerization upon irradiation with UV-light and visible light, while the substitution facilitates the high stability of the photochemically formed (Z)-isomer. The effectiveness of the irradiation and the composition of photostationary states was determined by UV/Vis and ¹H NMR spectroscopy. A nematic phase formed by the materials was characterized by differential scanning calorimetry and optical polarizing microscopy. We show that the materials easily change their relative configuration of the N=N double bond not only in solution, but also in the mesophase, which leads to fast isothermal phase transition from the nematic phase to isotropic liquid. Full article

(This article belongs to the Special Issue Photosensitive Liquid Crystals)

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9 pages, 7986 KiB

Open AccessEditor’s ChoiceArticle

The Curled Up Dimension in Quasicrystals

by Fang Fang, Richard Clawson and Klee Irwin

Crystals 2021, 11(10), 1238; https://doi.org/10.3390/cryst11101238 - 14 Oct 2021

Viewed by 3137

Abstract

Most quasicrystals can be generated by the cut-and-project method from higher dimensional parent lattices. In doing so they lose the periodic order their parent lattice possess, replaced with aperiodic order, due to the irrationality of the projection. However, perfect periodic order is discovered [...] Read more.

Most quasicrystals can be generated by the cut-and-project method from higher dimensional parent lattices. In doing so they lose the periodic order their parent lattice possess, replaced with aperiodic order, due to the irrationality of the projection. However, perfect periodic order is discovered in the perpendicular space when gluing the cut window boundaries together to form a curved loop. In the case of a 1D quasicrystal projected from a 2D lattice, the irrationally sloped cut region is bounded by two parallel lines. When it is extrinsically curved into a cylinder, a line defect is found on the cylinder. Resolving this geometrical frustration removes the line defect to preserve helical paths on the cylinder. The degree of frustration is determined by the thickness of the cut window or the selected pitch of the helical paths. The frustration can be resolved by applying a shear strain to the cut-region before curving into a cylinder. This demonstrates that resolving the geometrical frustration of a topological change to a cut window can lead to preserved periodic order. Full article

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29 pages, 24863 KiB

Open AccessEditor’s ChoiceArticle

Strain Localization Modes within Single Crystals Using Finite Deformation Strain Gradient Crystal Plasticity

by Lei Cai, Mohamed Jebahi and Farid Abed-Meraim

Crystals 2021, 11(10), 1235; https://doi.org/10.3390/cryst11101235 - 13 Oct 2021

Cited by 5 | Viewed by 2336

Abstract

The present paper aims at providing a comprehensive investigation of the abilities and limitations of strain gradient crystal plasticity (SGCP) theories in capturing different kinds of localization modes in single crystals. To this end, the small deformation Gurtin-type SGCP model recently proposed by [...] Read more.

The present paper aims at providing a comprehensive investigation of the abilities and limitations of strain gradient crystal plasticity (SGCP) theories in capturing different kinds of localization modes in single crystals. To this end, the small deformation Gurtin-type SGCP model recently proposed by the authors, based on non-quadratic defect energy and the uncoupled dissipation assumption, is extended to finite deformation. The extended model is then applied to simulate several single crystal localization problems with different slip system configurations. These configurations are chosen in such a way as to obtain idealized slip and kink bands as well as general localization bands, i.e., with no particular orientation with respect to the initial crystallographic directions. The obtained results show the good abilities of the applied model in regularizing various kinds of localization bands, except for idealized slip bands. Finally, the model is applied to reproduce the complex localization behavior of single crystals undergoing single slip, where competition between kink and slip bands can take place. Both higher-order energetic and dissipative effects are considered in this investigation. For both effects, mesh-independent results are obtained, proving the good capabilities of SGCP theories in regularizing complex localization behaviors. The results associated with higher-order energetic effects are in close agreement with those obtained using a micromorphic crystal plasticity approach. Higher-order dissipative effects led to different results with dominant slip banding. Full article

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15 pages, 7375 KiB

Open AccessEditor’s ChoiceArticle

Mesomorphic and Thermal Behavior of Symmetric Bent-Core Liquid Crystal Compounds Derived from Resorcinol and Isophthalic Acid

by Catalina Ionica Ciobanu, Iulian Berladean, Elena-Luiza Epure, Aurel Simion, Gabriela Lisa, Yahia Boussoualem and Irina Carlescu

Crystals 2021, 11(10), 1215; https://doi.org/10.3390/cryst11101215 - 8 Oct 2021

Cited by 3 | Viewed by 2237

Abstract

Bent-core liquid crystals (BCLC) have been widely studied as a result of their unusual polar and chiral properties. Similar to calamitic and discotic molecules, BCLC molecules also exhibit nematic phases, besides other higher order mesophases. The aim of this work is to comparatively [...] Read more.

Bent-core liquid crystals (BCLC) have been widely studied as a result of their unusual polar and chiral properties. Similar to calamitic and discotic molecules, BCLC molecules also exhibit nematic phases, besides other higher order mesophases. The aim of this work is to comparatively analyze the mesomorphic behavior of some bent-core 1,3-disubstituted benzene core compounds derived from resorcinol and isophthalic acid. Thus, the two classes of compounds differ in the nature of the orientation of the ester bond between the benzene central core and the two branches attached to the core. The mesomorphic behavior was elucidated by polarized light optical microscopy and differential calorimetry. Given the relatively high isotropic points of the compounds, confirmation of the thermal stability in the domains manifesting liquid crystalline properties was performed by thermogravimetric studies. The theoretical explanation of the difference in mesomorphic behavior for the two classes was based on molecular modeling studies. Full article

(This article belongs to the Special Issue Synthesis and Properties of Light-Emitting Liquid Crystals (Volume II))

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22 pages, 3834 KiB

Open AccessEditor’s ChoiceReview

On the Importance of σ–Hole Interactions in Crystal Structures

by Antonio Frontera and Antonio Bauzá

Crystals 2021, 11(10), 1205; https://doi.org/10.3390/cryst11101205 - 7 Oct 2021

Cited by 61 | Viewed by 5556

Abstract

Elements from groups 14–18 and periods 3–6 commonly behave as Lewis acids, which are involved in directional noncovalent interactions (NCI) with electron-rich species (lone pair donors), π systems (aromatic rings, triple and double bonds) as well as nonnucleophilic anions (BF₄⁻, [...] Read more.

Elements from groups 14–18 and periods 3–6 commonly behave as Lewis acids, which are involved in directional noncovalent interactions (NCI) with electron-rich species (lone pair donors), π systems (aromatic rings, triple and double bonds) as well as nonnucleophilic anions (BF₄⁻, PF₆⁻, ClO₄⁻, etc.). Moreover, elements of groups 15 to 17 are also able to act as Lewis bases (from one to three available lone pairs, respectively), thus presenting a dual character. These emerging NCIs where the main group element behaves as Lewis base, belong to the σ–hole family of interactions. Particularly (i) tetrel bonding for elements belonging to group 14, (ii) pnictogen bonding for group 15, (iii) chalcogen bonding for group 16, (iv) halogen bonding for group 17, and (v) noble gas bondings for group 18. In general, σ–hole interactions exhibit different features when moving along the same group (offering larger and more positive σ–holes) or the same row (presenting a different number of available σ–holes and directionality) of the periodic table. This is illustrated in this review by using several examples retrieved from the Cambridge Structural Database (CSD), especially focused on σ–hole interactions, complemented with molecular electrostatic potential surfaces of model systems. Full article

(This article belongs to the Special Issue Advanced Research in Halogen Bonding)

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14 pages, 4212 KiB

Open AccessEditor’s ChoiceArticle

DFT Calculation, Hirshfeld Analysis and X-Ray Crystal Structure of Some Synthesized N-alkylated(S-alkylated)-[1,2,4]triazolo[1,5-a]quinazolines

by Hatem A. Abuelizz, Saied M. Soliman, Hazem A. Ghabbour, Mohamed Marzouk, Mohamed M. Abdellatif and Rashad Al-Salahi

Crystals 2021, 11(10), 1195; https://doi.org/10.3390/cryst11101195 - 30 Sep 2021

Cited by 2 | Viewed by 2135

Abstract

The present work aimed to synthesize 2-methylthio-triazoloquinazoline derivatives and study their X-ray, NMR, DFT and Hirshfeld characteristics. The cyclocondensation of dimethyl-N-cyanodithiocarbonate with 2-hydrazinobenzoic acid hydrochloride resulted in an intermediate, 2-methylthio-[1,2,4]triazolo[1,5-a]quinazolin-5-one (A), which upon treatment with phosphorus pentasulfide, [...] Read more.

The present work aimed to synthesize 2-methylthio-triazoloquinazoline derivatives and study their X-ray, NMR, DFT and Hirshfeld characteristics. The cyclocondensation of dimethyl-N-cyanodithiocarbonate with 2-hydrazinobenzoic acid hydrochloride resulted in an intermediate, 2-methylthio-[1,2,4]triazolo[1,5-a]quinazolin-5-one (A), which upon treatment with phosphorus pentasulfide, transformed into the 2-methylthio-[1,2,4]triazolo[1,5-a]quinazolin-5-thione (B). Reaction of 2-methylthio-triazoloquinazolines (A&B) with alkyl halides (allyl bromide and ethyl iodide) in basic medium afforded 4-allyl-2-methylthio-[1,2,4]triazolo[1,5-a]quinazolin-5-one (1; N-alkylated) and 5-ethylthio-2-methylthio-[1,2,4]triazolo[1,5-a]quinazoline (2; S-alkylated), respectively. Their molecular and supramolecular structures were presented. Unambiguously, the molecular structures of 1 and 2 were confirmed via NMR and single-crystal X-ray diffraction. The resulting findings confirmed the structures of 1 and 2 and determined their crystalized system (monoclinic system; P2₁/n space group). Hirshfeld analysis of 1 revealed the importance of the significantly short O···H (6.7%), S···S (1.2%) and C···C (2.8%); however, the short H···H (42.6%), S···H (16.3%) and C···C (4.3%) were showed in 2 by intermolecular interactions in the molecular packing. The 1,2,4-triazoloquinzolines (1&2) were anticipated to be relatively polar compounds with net dipole moments of 2.9284 and 4.2127 Debye, respectively. The molecular electrostatic potential, atomic charge distribution maps and reactivity descriptors for 1 and 2 were also determined. The calculated nuclear magnetic resonance spectra of the targets 1 and 2 were well correlated with the experimental data. Full article

(This article belongs to the Special Issue Crystal Engineering: From Molecules to Crystals to Functional Materials)

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13 pages, 6799 KiB

Open AccessEditor’s ChoiceArticle

Impact of a Partial Solid Solution and Water Molecules on the Formation of Fibrous Crystals and Fluid Inclusions

by Laureline Marc, Chrystal Lopes, Jean-Marie Schneider, Morgane Sanselme and Gérard Coquerel

Crystals 2021, 11(10), 1188; https://doi.org/10.3390/cryst11101188 - 29 Sep 2021

Cited by 7 | Viewed by 2776

Abstract

Resolution of (±)ibuprofen using S-α-Methylbenzylamine in pure ethanol leads to the enriched S-IBU/S-αMBA diastereomeric salt which crystallizes as very fine needles. In order to improve the filterability and processability of the solid phase, water can be added to the medium and lead to [...] Read more.

Resolution of (±)ibuprofen using S-α-Methylbenzylamine in pure ethanol leads to the enriched S-IBU/S-αMBA diastereomeric salt which crystallizes as very fine needles. In order to improve the filterability and processability of the solid phase, water can be added to the medium and lead to more equant particles that are still elongated. A high fraction of the resulting platelets display on both ends a fluid inclusion containing both liquid and a large bubble of gas. A detailed analysis of the particles reveals that they are not really single crystals but more an ordered association of fibers defined as fibrous crystal. A domain of partial solid solution is evidenced near the pure less soluble diastereomer and its impact on the formation of fibrous crystals is demonstrated. When pure S-IBU/S-αMBA diastereomeric salt is recrystallized in the same medium (e.g., ethanol–water) the crystallinity is improved, but fluid inclusions can still be observed. Full article

(This article belongs to the Special Issue Crystal Nucleation and Growth Kinetics)

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12 pages, 5203 KiB

Open AccessEditor’s ChoiceArticle

Ferroelectric Properties and Spectroscopic Characterization of Pb(Mg_1/3Nb_2/3)O₃-32PbTiO₃:Er³⁺/Sc³⁺ Crystal

by Jin Zhang, Zengzhe Xi, Xinzhe Wang, Hao Feng, Wei Long and Aiguo He

Crystals 2021, 11(10), 1155; https://doi.org/10.3390/cryst11101155 - 23 Sep 2021

Viewed by 2335

Abstract

An Er³⁺/Sc³⁺ co-doped 0.68Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ ferroelectric single crystal was grown by high-temperature flux method. The remnant polarization Pr is 27.97 µC/cm² and the coercive field Ec is 8.26 kV/cm for [100] oriented crystal. [...] Read more.

An Er³⁺/Sc³⁺ co-doped 0.68Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ ferroelectric single crystal was grown by high-temperature flux method. The remnant polarization Pr is 27.97 µC/cm² and the coercive field Ec is 8.26 kV/cm for [100] oriented crystal. Green (524 and 551 nm) and red (654 nm) emission bands are generated at the 980 nm excitation, which corresponds to the ²H_11/2→ ⁴I_15/2, ⁴S_3/2→ ⁴I_15/2 and ⁴F_9/2→ ⁴I_15/2 transitions of Er³⁺, respectively. Judd–Ofelt theory has been applied to predict the spectroscopic characteristics of the as-grown crystals. The obtained J–O intensity parameters Ω_t (t = 2, 4 and 6) are Ω₂ = 0.76 × 10⁻²⁰ cm², Ω₄ = 1.0 × 10⁻²⁰ cm², Ω₆ = 0.55 × 10⁻²⁰ cm². Spectroscopic characteristics, including optical transition probabilities, branching ratio, and radiative lifetime of Er³⁺ in the crystal, are determined. The calculated radiative lifetimes of ⁴I_13/2 and ⁴I_11/2 energy levels are 2.82 ms and 2.61 ms, respectively. These investigations provide possibilities for the crystal Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃:Er³⁺/Sc³⁺ to be a new type of multifunctional crystal integrating electricity-luminescence. Full article

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8 pages, 2171 KiB

Open AccessEditor’s ChoiceArticle

Multi-Component Crystals of 2,2′-Bipyridine with Aliphatic Dicarboxylic Acids: Melting Point-Structure Relations

by Vhukhudo Nethanani and Eustina Batisai

Crystals 2021, 11(10), 1151; https://doi.org/10.3390/cryst11101151 - 22 Sep 2021

Viewed by 2455

Abstract

The aim of the study was to investigate the relationship between the melting point and the supramolecular structure of three multi-component crystals of aliphatic dicarboxylic acids with 2,2′-bipyridine and to investigate the conformations of 2,2′-bipyridine in published multi-component crystals. The crystals were prepared [...] Read more.

The aim of the study was to investigate the relationship between the melting point and the supramolecular structure of three multi-component crystals of aliphatic dicarboxylic acids with 2,2′-bipyridine and to investigate the conformations of 2,2′-bipyridine in published multi-component crystals. The crystals were prepared using the solvent evaporation method and were characterized using single-crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), and differential scanning calorimetry (DSC). The crystal structures were further analyzed using CrystalExplorer, and the results were correlated with the melting points. The results of the conformation analysis of the reported multi-component crystals of 2,2′-bipyridine are also presented. Full article

(This article belongs to the Section Crystal Engineering)

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10 pages, 3112 KiB

Open AccessEditor’s ChoiceArticle

Bandgap and Carrier Dynamic Controls in CsPbBr₃ Nanocrystals Encapsulated in Polydimethylsiloxane

by Lianxing Liao, Kunhua Quan, Xiangshi Bin, Ruosheng Zeng and Tao Lin

Crystals 2021, 11(9), 1132; https://doi.org/10.3390/cryst11091132 - 17 Sep 2021

Cited by 4 | Viewed by 3235

Abstract

Bandgap tunability through ion substitution is a key feature of lead halide perovskite nanocrystals (LHP-NCs). However, the low stability and low luminescent performance of CsPbCl₃ hinder their full-color applications. In this work, quantum confinement effect (QCE) was utilized to control the bandgap [...] Read more.

Bandgap tunability through ion substitution is a key feature of lead halide perovskite nanocrystals (LHP-NCs). However, the low stability and low luminescent performance of CsPbCl₃ hinder their full-color applications. In this work, quantum confinement effect (QCE) was utilized to control the bandgap of CsPbBr₃ NCs instead of using unstable CsPbCl₃, which possess much higher emission efficiency in blue spectra region. Studies of microstructures, optical spectra and carrier dynamics revealed that tuning the reaction temperature was an effective way of controlling the NC sizes as well as QCE. Furthermore, the obtained CsPbBr₃ NCs were encapsulated in a PDMS matrix while maintaining their size distribution and quantum-confined optoelectronic properties. The encapsulated samples showed long-term air and water stability. These results provide valuable guidance for both applications of LHP-NCs and principal investigation related to the carrier transition in LHP-NCs. Full article

(This article belongs to the Section Materials for Energy Applications)

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18 pages, 3542 KiB

Open AccessEditor’s ChoiceReview

Advances of Yb:CALGO Laser Crystals

by Hao Wang, Jing Pan, Yuan Meng, Qiang Liu and Yijie Shen

Crystals 2021, 11(9), 1131; https://doi.org/10.3390/cryst11091131 - 17 Sep 2021

Cited by 11 | Viewed by 5932

Abstract

Yb:CaGdAlO₄, or Yb:CALGO, a new laser crystal, has been attracting increasing attention recently in a myriad of laser technologies. This crystal features salient thermal, spectroscopic and mechanical properties, which enable highly efficient and safe generation of continuous-wave radiations and ultrafast pulses [...] Read more.

Yb:CaGdAlO₄, or Yb:CALGO, a new laser crystal, has been attracting increasing attention recently in a myriad of laser technologies. This crystal features salient thermal, spectroscopic and mechanical properties, which enable highly efficient and safe generation of continuous-wave radiations and ultrafast pulses with ever short durations. More specifically, its remarkable thermal-optic property and its high conversion efficiency allow high-power operation. Its high nonlinear coefficient facilitates study of optimized mode locking lasers. Besides, its ultrabroad and flat-top emission band benefits the generation of complex structured light with outstanding tunability. In this paper, we review the recent advances in the study of Yb:CALGO, covering its physical properties as well as its growing applications in various fields and prospect for future development. Full article

(This article belongs to the Special Issue Advanced Laser Technology and Applications)

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12 pages, 5334 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Spatial Structures and Packaging of Phosphorybosil Pyrophosphate Synthetase 2 from Thermus thermophilus HB27 in Rhombohedral and Tetragonal Crystals

by Yulia Abramchik, Evgeniy Zayats, Maria Kostromina, Dmitry Lykoshin, Ilya Fateev, Irina Konstantinova, Nadezda Zhukhlistova, Vladimir Timofeev, Inna Kuranova and Roman Esipov

Crystals 2021, 11(9), 1128; https://doi.org/10.3390/cryst11091128 - 16 Sep 2021

Cited by 1 | Viewed by 2189

Abstract

We report the spatial structure of phosphoribosyl pyrophosphate synthetase 2 from the thermophilic bacterium Thermus thermophilus HB27 (TthPRPPS2) obtained at a 1.85 Å resolution using a diffraction set collected from rhombohedral crystals (space group R3₂-h), grown with lithium sulfate as [...] Read more.

We report the spatial structure of phosphoribosyl pyrophosphate synthetase 2 from the thermophilic bacterium Thermus thermophilus HB27 (TthPRPPS2) obtained at a 1.85 Å resolution using a diffraction set collected from rhombohedral crystals (space group R3₂-h), grown with lithium sulfate as a precipitant. This crystal structure was compared with the structure of TthPRPPS2, previously obtained at a 2.2 Å resolution using diffraction sets from the tetragonal crystals (space group P4₁2₁2), grown with ammonium sulfate as a precipitant. The comparison of these structures allows the study of the differences between protein molecules in both crystalline structures, as well as the packaging of enzyme molecules in crystals of both spatial groups. Our results may contribute to the research of the structural basis of catalytic activity and substrate specificity of this enzyme. Full article

(This article belongs to the Section Biomolecular Crystals)

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15 pages, 8295 KiB

Open AccessEditor’s ChoiceArticle

Thermal Deformations of Crystal Structures in the L-Aspartic Acid/L-Glutamic Acid System and DL-Aspartic Acid

by Roman Sadovnichii, Elena Kotelnikova and Heike Lorenz

Crystals 2021, 11(9), 1102; https://doi.org/10.3390/cryst11091102 - 10 Sep 2021

Cited by 2 | Viewed by 2513

Abstract

The method of temperature-resolved powder X-ray diffraction (TRPXRD) was used to determine the elevated temperature behavior of L-aspartic acid (L-asp), DL-aspartic acid (DL-asp), L-glutamic acid (L-glu), and an L-asp_0.25,L-glu_0.75 solid solution. These amino acids were not found to undergo any [...] Read more.

The method of temperature-resolved powder X-ray diffraction (TRPXRD) was used to determine the elevated temperature behavior of L-aspartic acid (L-asp), DL-aspartic acid (DL-asp), L-glutamic acid (L-glu), and an L-asp_0.25,L-glu_0.75 solid solution. These amino acids were not found to undergo any solid-phase (polymorph) transformations. When heated, they all experienced only thermal deformations. The corresponding parameters of the monoclinic cells of L-asp and DL-asp, and the orthorhombic cells of L-glu and L-asp_0.25,L-glu_0.75, were calculated for the entire range of studied temperatures (up to 220 °C). The data obtained were used to calculate the parameters of the thermal deformation tensors, and to plot the figures of their thermal expansion coefficients. A correlation between the maximum and minimum values of thermal expansion coefficients and the length, type, direction, and number of hydrogen bonds in the crystal structures of the investigated amino acids was established. The observed negative thermal expansion (contraction) of crystal structures of L-asp and DL-asp along the ac plane can be explained as a result of shear deformations occurring in monoclinic crystals with a non-fixed angle β. The studies were related to the presence of amino acids in various natural and technological processes occurring at different temperatures. Full article

(This article belongs to the Special Issue Recent Progress in Industrial Crystallization)

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13 pages, 2827 KiB

Open AccessEditor’s ChoiceArticle

Remarkable Increase of Fluorescence Quantum Efficiency by Cyano Substitution on an ESIPT Molecule 2-(2-Hydroxyphenyl)benzothiazole: A Highly Photoluminescent Liquid Crystal Dopant

by Tsuneaki Sakurai, Masaya Kobayashi, Hiroyuki Yoshida and Masaki Shimizu

Crystals 2021, 11(9), 1105; https://doi.org/10.3390/cryst11091105 - 10 Sep 2021

Cited by 16 | Viewed by 4152

Abstract

Fluorescent molecules with excited-state intramolecular proton transfer (ESIPT) character allow the efficient solid-state luminescence with large Stokes shift that is important for various applications, such as organic electronics, photonics, and bio-imaging fields. However, the lower fluorescence quantum yields (Φ_FL) in [...] Read more.

Fluorescent molecules with excited-state intramolecular proton transfer (ESIPT) character allow the efficient solid-state luminescence with large Stokes shift that is important for various applications, such as organic electronics, photonics, and bio-imaging fields. However, the lower fluorescence quantum yields (Φ_FL) in the solution or viscous media, due to their structural relaxations in the excited state to reach the S₀/S₁ conical intersection, shackle further applications of ESIPT-active luminophores. Here we report that the introduction of a cyano group (-CN) into the phenyl group of 2-(2-hydroxyphenyl)benzothiazole (HBT), a representative ESIPT compound, remarkably increase its fluorescence quantum yield (Φ_FL) from 0.01 (without -CN) to 0.49 (with -CN) in CH₂Cl₂, without disturbing its high Φ_FL (=0.52) in the solid state. The large increase of the solution-state Φ_FL of the cyano-substituted HBT (CN-HBT) is remarkable, comparing with our previously reported Φ_FL values of 0.05 (with 4-pentylphenyl), 0.07 (with 1-hexynyl), and 0.15 (with 4-pentylphenylethynyl). Of interest, the newly-synthesized compound, CN-HBT, is miscible in a conventional room-temperature nematic liquid crystal (LC), 4-pentyl-4′-cyano biphenyl (5CB), up to 1 wt% (~1 mol%), and exhibits a large Φ_FL of 0.57 in the viscous LC medium. A similar Φ_FL value of Φ_FL = 0.53 was also recorded in another room-temperature LC, trans-4-(4-pentylcyclohexyl)benzonitrile (PCH5), with a doping ratio of 0.5 wt% (~0.5 mol%). These 5CB/CN-HBT and PCH5/CN-HBT mixtures serve as light-emitting room-temperature LCs, and show anisotropic fluorescence with the dichroic ratio of 3.1 upon polarized excitation, as well as electric field response of luminescence intensity changes. Full article

(This article belongs to the Special Issue Synthesis and Properties of Light-Emitting Liquid Crystals (Volume II))

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12 pages, 596 KiB

Open AccessEditor’s ChoiceArticle

The Refraction Indices and Brewster Law in Stressed Isotropic Materials and Cubic Crystals

by Daniele Rinaldi, Pier Paolo Natali, Luigi Montalto and Fabrizio Davì

Crystals 2021, 11(9), 1104; https://doi.org/10.3390/cryst11091104 - 10 Sep 2021

Cited by 2 | Viewed by 2017

Abstract

We study the elasto-optic behavior of stressed cubic crystals (all classes) and isotropic materials (like e.g., glasses). We obtain the explicit dependence of the refraction indices on the stress (either applied or residual), as well as a mild generalization of the Brewster law [...] Read more.

We study the elasto-optic behavior of stressed cubic crystals (all classes) and isotropic materials (like e.g., glasses). We obtain the explicit dependence of the refraction indices on the stress (either applied or residual), as well as a mild generalization of the Brewster law for cubic crystals. We show also that the optic indicatrix and the stress ellipsoid are coaxial only in the isotropic case. This theory allows the improvement of the measurement techniques, as photoelasticity, on cubic crystals and optically isotropic materials. Full article

(This article belongs to the Special Issue Photoelasticity in Optical Media from Crystals to Amorphous Materials)

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9 pages, 2340 KiB

Open AccessEditor’s ChoiceArticle

Optically Tunable Terahertz Metasurfaces Using Liquid Crystal Cells Coated with Photoalignment Layers

by Yi-Hong Shih, Xin-Yu Lin, Harry Miyosi Silalahi, Chia-Rong Lee and Chia-Yi Huang

Crystals 2021, 11(9), 1100; https://doi.org/10.3390/cryst11091100 - 10 Sep 2021

Cited by 8 | Viewed by 3077

Abstract

An optically tunable terahertz filter was fabricated using a metasurface-imbedded liquid crystal (LC) cell with photoalignment layers in this work. The LC director in the cell is aligned by a pump beam and makes angles θ of 0, 30, 60 and 90° with [...] Read more.

An optically tunable terahertz filter was fabricated using a metasurface-imbedded liquid crystal (LC) cell with photoalignment layers in this work. The LC director in the cell is aligned by a pump beam and makes angles θ of 0, 30, 60 and 90° with respect to the gaps of the split-ring resonators (SRRs) of the metasurface under various polarized directions of the pump beam. Experimental results display that the resonance frequency of the metasurface in the cell increases with an increase in θ, and the cell has a frequency tuning region of 15 GHz. Simulated results reveal that the increase in the resonance frequency arises from the birefringence of the LC, and the LC has a birefringence of 0.13 in the terahertz region. The resonance frequency of the metasurface is shifted using the pump beam, so the metasurface-imbedded LC cell with the photoalignment layers is an optically tunable terahertz filter. The optically tunable terahertz filter is promising for applications in terahertz telecommunication, biosensing and terahertz imaging. Full article

(This article belongs to the Special Issue Liquid Crystal Optics for Applications)

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14 pages, 921 KiB

Open AccessEditor’s ChoiceArticle

Photoelastic Properties of Trigonal Crystals

by Bohdan Mytsyk, Nataliya Demyanyshyn, Anatoliy Andrushchak and Oleh Buryy

Crystals 2021, 11(9), 1095; https://doi.org/10.3390/cryst11091095 - 8 Sep 2021

Cited by 5 | Viewed by 2677

Abstract

All possible experimental geometries of the piezo-optic effect in crystals of trigonal symmetry are studied in detail through the interferometric technique, and the corresponding expressions for the calculation of piezo-optic coefficients (POCs) π_im and some sums of π_im based on experimental [...] Read more.

All possible experimental geometries of the piezo-optic effect in crystals of trigonal symmetry are studied in detail through the interferometric technique, and the corresponding expressions for the calculation of piezo-optic coefficients (POCs) π_im and some sums of π_im based on experimental data obtained from the samples of direct and X/45°-cuts are given. The reliability of the values of POCs is proven by the convergence of π_im obtained from different experimental geometries as well as by the convergence of some sums of POCs. Because both the signs and the absolute values of POCs π₁₄ and π₄₁ are defined by the choice of the right crystal-physics coordinate system, we here use the system whereby the condition S₁₄ > 0 is fulfilled (S₁₄ is an elastic compliance coefficient). The absolute value and the sign of S₁₄ are determined by piezo-optic interferometric method from two experimental geometries. The errors of POCs are calculated as mean square values of the errors of the half-wave stresses and the elastic term. All components of the matrix of elasto-optic coefficients p_in are calculated based on POCs and elastic stiffness coefficients. The technique is tested on LiTaO₃ crystal. The obtained results are compared with the corresponding data for trigonal LiNbO₃ and Ca₃TaGa₃Si₂O₁₄ crystals. Full article

(This article belongs to the Special Issue Photoelasticity in Optical Media from Crystals to Amorphous Materials)

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12 pages, 2687 KiB

Open AccessEditor’s ChoiceArticle

Scanning Electron Microscopy Investigation of Surface Acoustic Wave Propagation in a 41° YX-Cut of a LiNbO₃ Crystal/Si Layered Structure

by Dmitry Roshchupkin, Evgenii Emelin, Olga Plotitcina, Anatoly Mololkin and Oleg Telminov

Crystals 2021, 11(9), 1082; https://doi.org/10.3390/cryst11091082 - 6 Sep 2021

Cited by 5 | Viewed by 2704

Abstract

The propagation process of the surface acoustic waves (SAW) and the pseudo-surface acoustic waves (PSAW) in a bonded layered structure of a 41° YX-cut of a LiNbO₃ crystal/Si(100) crystal was investigated. The scanning electron microscopy (SEM) method,in the low-energy secondary electrons registration [...] Read more.

The propagation process of the surface acoustic waves (SAW) and the pseudo-surface acoustic waves (PSAW) in a bonded layered structure of a 41° YX-cut of a LiNbO₃ crystal/Si(100) crystal was investigated. The scanning electron microscopy (SEM) method,in the low-energy secondary electrons registration mode, made it possible to visualize the SAW and PSAW in the LiNbO₃/Si layered structure. The process of the SAW and PSAW propagation in a LiNbO₃/Si layered structure and in a bulk 41° YX-cut of a LiNbO₃ crystal were compared. It was demonstrated that the SAW velocities in the layered LiNbO₃/Si structure exceed the typical SAW velocities for LiNbO₃ and Si single crystals. In the layered structure, the SAW and PSAW velocities were 4062 m/s, 4731 m/s, and 5871 m/s. It was also demonstrated that the PSAW velocities are the same in the LiNbO₃/Si layered structure and in the bulk 41° YX-cut of a LiNbO₃ crystal. Full article

(This article belongs to the Special Issue Ferroelectric and Piezoelectric Crystals)

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19 pages, 3321 KiB

Open AccessEditor’s ChoiceArticle

Synthesis, Crystal Structure, Inhibitory Activity and Molecular Docking of Coumarins/Sulfonamides Containing Triazolyl Pyridine Moiety as Potent Selective Carbonic Anhydrase IX and XII Inhibitors

by Yassine Aimene, Romain Eychenne, Frédéric Rodriguez, Sonia Mallet-Ladeira, Nathalie Saffon-Merceron, Jean-Yves Winum, Alessio Nocentini, Claudiu T. Supuran, Eric Benoist and Achour Seridi

Crystals 2021, 11(9), 1076; https://doi.org/10.3390/cryst11091076 - 6 Sep 2021

Cited by 14 | Viewed by 4146

Abstract

In this work, two classes of Carbonic Anhydrase (CA) inhibitors, sulfonamide and coumarin derivatives linked to pyta moiety (2a-b) and their corresponding rhenium complexes (3a-b), were designed. These compounds were synthesized and fully characterized by classical analytical methods and [...] Read more.

In this work, two classes of Carbonic Anhydrase (CA) inhibitors, sulfonamide and coumarin derivatives linked to pyta moiety (2a-b) and their corresponding rhenium complexes (3a-b), were designed. These compounds were synthesized and fully characterized by classical analytical methods and X-ray diffraction. All the synthesized compounds were evaluated for their inhibitory activity against the hCA isoforms I, II, IX and XII. They exhibited high inhibitory activities in the range of nanomolar for both hCA IX and hCA XII isoforms. The sulfonamide compound 2a showed the strongest inhibition against the tumour-associated hCA IX isoform with a Ki of 11.7 nM. The tumour-associated isoforms hCA IX and hCA XII were selectively inhibited by all the coumarin derivatives, with inhibition constants ranging from 12.7 nM (2b) to 44.5 nM (3b), while the hCA I and II isoforms were slightly inhibited (in the micromolar range), as expected. In terms of selectivity, compared to previously published rhenium complex-based CA inhibitors, complex 3b showed one of the highest selectivities against hCA IX and hCA XII compared to the off-target isoforms hCA I and hCA II, making it a potential anti-cancer drug candidate. Molecular docking calculations were performed to investigate the inhibition profiles of the investigated compounds at the tumour-associated hCA IX active site and to rationalize our results. Full article

(This article belongs to the Special Issue Discovery, Modeling, Synthesis and Performance Evaluation of Enzyme Inhibitors)

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12 pages, 1855 KiB

Open AccessEditor’s ChoiceArticle

Growth of Acetaminophen Polymorphic Crystals and Solution-Mediated Phase Transition from Trihydrate to Form II in Agarose Gel

by Akari Nishigaki, Mihoko Maruyama, Shun-ichi Tanaka, Hiroshi Y. Yoshikawa, Masayuki Imanishi, Masashi Yoshimura, Yusuke Mori and Kazufumi Takano

Crystals 2021, 11(9), 1069; https://doi.org/10.3390/cryst11091069 - 5 Sep 2021

Cited by 2 | Viewed by 2871

Abstract

The growth of acetaminophen polymorphic crystals and the solution-mediated phase transition from trihydrate to form II in agarose gel were investigated. The form II crystals grown in gels, presumably because of the agarose content, dissolved less rapidly at high temperatures and were more [...] Read more.

The growth of acetaminophen polymorphic crystals and the solution-mediated phase transition from trihydrate to form II in agarose gel were investigated. The form II crystals grown in gels, presumably because of the agarose content, dissolved less rapidly at high temperatures and were more stable than in water. The trihydrate crystals in the gel were also expected to be stabilized by containing agarose, but in fact the fine morphology resulted in reduced stability. The solution-mediated phase transition from trihydrate to form II via form II seeding took longer in the gel because the gel slowed down the dissolution of the trihydrate by hindering the dispersion of the form II seeds and delayed the growth of form II by reducing the diffusion rate of the molecules dissolved from the trihydrate. Delays in solution-mediated phase transition and changes in stability for crystals grown in gels indicate the effectiveness of gels in controlling polymorphisms in pharmaceutical compounds. Full article

(This article belongs to the Special Issue Crystallization Processes: Food and Pharmaceutical Crystals)

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12 pages, 4047 KiB

Open AccessEditor’s ChoiceArticle

Control of Crystallographic Texture and Mechanical Properties of Hastelloy-X via Laser Powder Bed Fusion

by Shinya Hibino, Tsubasa Todo, Takuya Ishimoto, Ozkan Gokcekaya, Yuichiro Koizumi, Kenichiroh Igashira and Takayoshi Nakano

Crystals 2021, 11(9), 1064; https://doi.org/10.3390/cryst11091064 - 3 Sep 2021

Cited by 29 | Viewed by 4268

Abstract

The influence of various laser powder bed fusion (LPBF) process parameters on the crystallographic textures and mechanical properties of a typical Ni-based solid-solution strengthened alloy, Hastelloy-X, was examined. Samples were classified into four groups based on the type of crystallographic texture: single crystalline-like [...] Read more.

The influence of various laser powder bed fusion (LPBF) process parameters on the crystallographic textures and mechanical properties of a typical Ni-based solid-solution strengthened alloy, Hastelloy-X, was examined. Samples were classified into four groups based on the type of crystallographic texture: single crystalline-like microstructure with <100>//build direction (BD) (<100>-SCM), single crystalline-like microstructure with <110>//BD (<110>-SCM), crystallographic lamellar microstructure (CLM), or polycrystalline microstructure (PCM). These four crystallographic textures were realized in Hastelloy-X for the first time here to the best of our knowledge. The mechanical properties of the samples varied depending on their texture. The tensile properties were affected not only by the Schmid factor but also by the grain size and the presence of lamellar boundaries (grain boundaries). The lamellar boundaries at the interface between the <110>//BD oriented main layers and the <100>//BD-oriented sub-layers of CLM contributed to the resistance to slip transmission and the increased proof stress. It was possible to control a wide range of crystallographic microstructures via the LPBF process parameters, which determines the melt pool morphology and solidification behavior. Full article

(This article belongs to the Special Issue Additive Manufacturing: Materials, Processing, Characterization and Applications)

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10 pages, 2592 KiB

Open AccessEditor’s ChoiceReview

Optically Rewritable Liquid Crystal Displays: Characteristics and Performance

by Vladimir G. Chigrinov, Aleksey A. Kudreyko and Fedor V. Podgornov

Crystals 2021, 11(9), 1053; https://doi.org/10.3390/cryst11091053 - 1 Sep 2021

Cited by 5 | Viewed by 2724

Abstract

Recent achievements in the photoalignment technique for fabrication of optically rewritable electronic paper with high performance characteristics are surveyed with emphasis on temporal constraints on the exposure process. The possibility of creating electrode-free electronic paper has very important practical aspects. However, many existing [...] Read more.

Recent achievements in the photoalignment technique for fabrication of optically rewritable electronic paper with high performance characteristics are surveyed with emphasis on temporal constraints on the exposure process. The possibility of creating electrode-free electronic paper has very important practical aspects. However, many existing studies do not include sufficient analysis on how to achieve acceptable reflective characteristics within short exposure time. In order to achieve this goal, we have applied the rotational diffusion model. We find that the parameters of the diffusion model can be adjusted to get acceptable light-reflecting characteristics within 10 s of exposure. In comparison with the long-time exposure, the reflectance coefficient reduces by 24%. The route to material improvements for optimized e-paper device is discussed. Full article

(This article belongs to the Special Issue Liquid Crystals in China)

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7 pages, 676 KiB

Open AccessEditor’s ChoiceCommunication

Using DFT to Calculate the Parameters of the Crystal Field in Mn²⁺ Doped Hydroxyapatite Crystals

by Daria Vladimirovna Shurtakova, Peter Olegovich Grishin, Marat Revgerovich Gafurov and Georgy Vladimirovich Mamin

Crystals 2021, 11(9), 1050; https://doi.org/10.3390/cryst11091050 - 31 Aug 2021

Cited by 9 | Viewed by 3315

Abstract

Crystal field parameters for two nonequivalent positions Ca (I) and Ca (II) for hydroxyapatite (HAp) crystals from the density functional theory (DFT) are calculated. Calculations are compared with the experimental electron paramagnetic resonance (EPR) spectra (registered at two microwave frequencies) for the synthesized [...] Read more.

Crystal field parameters for two nonequivalent positions Ca (I) and Ca (II) for hydroxyapatite (HAp) crystals from the density functional theory (DFT) are calculated. Calculations are compared with the experimental electron paramagnetic resonance (EPR) spectra (registered at two microwave frequencies) for the synthesized Mn-HAp powders Ca₉.₉₉₅Mn₀.₀₀₅(PO₄)₆(OH)₂. It is found that in the investigated species, the manganese is redistributed between both calcium sites with prevalence in Ca (I). Agreement between the calculated and experimental data proves that crystal field parameters in HAp can be calculated in the classical DFT model using the distributed electron density. Full article

(This article belongs to the Special Issue Hydroxyapatite Base Nanocomposites (Volume II))

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16 pages, 2644 KiB

Open AccessEditor’s ChoiceArticle

Crystal-Site-Based Artificial Neural Networks for Material Classification

by Juan I. Gómez-Peralta, Nidia G. García-Peña and Xim Bokhimi

Crystals 2021, 11(9), 1039; https://doi.org/10.3390/cryst11091039 - 29 Aug 2021

Cited by 3 | Viewed by 4970

Abstract

In materials science, crystal structures are the cornerstone in the structure–property paradigm. The description of crystal compounds may be ascribed to the number of different atomic chemical environments, which are related to the Wyckoff sites. Hence, a set of features related to the [...] Read more.

In materials science, crystal structures are the cornerstone in the structure–property paradigm. The description of crystal compounds may be ascribed to the number of different atomic chemical environments, which are related to the Wyckoff sites. Hence, a set of features related to the different atomic environments in a crystal compound can be constructed as input data for artificial neural networks (ANNs). In this article, we show the performance of a series of ANNs developed using crystal-site-based features. These ANNs were developed to classify compounds into halite, garnet, fluorite, hexagonal perovskite, ilmenite, layered perovskite, -o-tp- perovskite, perovskite, and spinel structures. Using crystal-site-based features, the ANNs were able to classify the crystal compounds with a 93.72% average precision. Furthermore, the ANNs were able to retrieve missing compounds with one of these archetypical structure types from a database. Finally, we showed that the developed ANNs were also suitable for a multitask learning paradigm, since the extracted information in the hidden layers linearly correlated with lattice parameters of the crystal structures. Full article

(This article belongs to the Special Issue Applications of Machine Learning to the Study of Crystalline Materials)

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12 pages, 895 KiB

Open AccessEditor’s ChoiceArticle

Tunable Bandgaps in Phononic Crystal Microbeams Based on Microstructure, Piezo and Temperature Effects

by Jun Hong, Zhuangzhuang He, Gongye Zhang and Changwen Mi

Crystals 2021, 11(9), 1029; https://doi.org/10.3390/cryst11091029 - 26 Aug 2021

Cited by 14 | Viewed by 2387

Abstract

A new model of non-classical phononic crystal (PC) microbeam for the elastic wave bandgap generation is provided, incorporating microstructure, piezomagnetism, piezoelectricity and temperature effects. The wave equation of a general magneto–electro–elastic (MEE) phononic crystal microbeam is derived, which recovers piezoelectric- and piezomagnetic-based counterparts [...] Read more.

A new model of non-classical phononic crystal (PC) microbeam for the elastic wave bandgap generation is provided, incorporating microstructure, piezomagnetism, piezoelectricity and temperature effects. The wave equation of a general magneto–electro–elastic (MEE) phononic crystal microbeam is derived, which recovers piezoelectric- and piezomagnetic-based counterparts as special cases. The piezomagnetic and piezoelectric materials are periodically combined to construct the PC microbeam and corresponding bandgaps are obtained by using the plane wave expansion (PWE) method. The effects of the piezomagnetism, piezoelectricity, microstructure, geometrical parameters and applied multi-fields (e.g., external electric potential, external magnetic potential, temperature change) on the bandgaps are discussed. The numerical results reveal that the bandgap frequency is raised with the presence of piezo and microstructure effects. In addition, the geometry parameters play an important role on the bandgap. Furthermore, large bandgaps can be realized by adjusting the external electric and magnetic potentials at micron scale, and lower bandgap frequency can be realized through the temperature rise at all length scales. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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25 pages, 8705 KiB

Open AccessEditor’s ChoiceArticle

Crystal Structure, Vibrational, Spectroscopic and Thermochemical Properties of Double Sulfate Crystalline Hydrate [CsEu(H₂O)₃(SO₄)₂]·H₂O and Its Thermal Dehydration Product CsEu(SO₄)₂

by Yuriy G. Denisenko, Maxim S. Molokeev, Aleksandr S. Oreshonkov, Alexander S. Krylov, Aleksandr S. Aleksandrovsky, Nikita O. Azarapin, Oleg V. Andreev, Illaria A. Razumkova and Victor V. Atuchin

Crystals 2021, 11(9), 1027; https://doi.org/10.3390/cryst11091027 - 26 Aug 2021

Cited by 54 | Viewed by 4388

Abstract

Crystalline hydrate of double cesium europium sulfate [CsEu(H₂O)₃(SO₄)₂]·H₂O was synthesized by the crystallization from an aqueous solution containing equimolar amounts of 1Cs⁺:1Eu³⁺:2SO₄²⁻ ions. Anhydrous salt CsEu(SO₄ [...] Read more.

Crystalline hydrate of double cesium europium sulfate [CsEu(H₂O)₃(SO₄)₂]·H₂O was synthesized by the crystallization from an aqueous solution containing equimolar amounts of 1Cs⁺:1Eu³⁺:2SO₄²⁻ ions. Anhydrous salt CsEu(SO₄)₂ was formed as a result of the thermal dehydration of the crystallohydrate. The unusual effects observed during the thermal dehydration were attributed to the specific coordination of water molecules in the [CsEu(H₂O)₃(SO₄)₂]·H₂O structure. The crystal structure of [CsEu(H₂O)₃(SO₄)₂]·H₂O was determined by a single crystal X-ray diffraction analysis, and the crystal structure of CsEu(SO₄)₂ was obtained by the Rietveld method. [CsEu(H₂O)₃(SO₄)₂]·H₂O crystallizes in the monoclinic system, space group P2₁/c (a = 6.5574(1) Å, b = 19.0733(3) Å, c = 8.8364(2) Å, β = 93.931(1)°, V = 1102.58(3) Å3). The anhydrous sulfate CsEu(SO₄)₂ formed as a result of the thermal destruction crystallizes in the monoclinic system, space group C2/c (a = 14.327(1) Å, b = 5.3838(4) Å, c = 9.5104(6) Å, β = 101.979(3) °, V = 717.58(9) Å3). The vibration properties of the compounds are fully consistent with the structural models and are mainly determined by the deformation of non-rigid structural elements, such as H₂O and SO₄²⁻. As shown by the diffused reflection spectra measurements and DFT calculations, the structural transformation from [CsEu(H₂O)₃(SO₄)₂]·H₂O to CsEu(SO₄)₂ induced a significant band gap reduction. A noticeable difference of the luminescence spectra between cesium europium sulfate and cesium europium sulfate hydrate is detected and explained by the variation of the extent of local symmetry violation at the crystallographic sites occupied by Eu³⁺ ions, namely, by the increase in inversion asymmetry in [CsEu(H2O)₃(SO₄)₂]·H₂O and the increase in mirror asymmetry in CsEu(SO₄)₂. The chemical shift of the ⁵D₀ energy level in cesium europium sulfate hydrate, with respect to cesium europium sulfate, is associated with the presence of H₂O molecules in the vicinity of Eu³⁺ ion. Full article

(This article belongs to the Special Issue Raman Spectroscopy of Crystals Volume II)

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16 pages, 8742 KiB

Open AccessEditor’s ChoiceReview

A Review of Two-Dimensional Liquid Crystal Polarization Gratings

by Kai Zuo, Yue Shi and Dan Luo

Crystals 2021, 11(9), 1015; https://doi.org/10.3390/cryst11091015 - 25 Aug 2021

Cited by 10 | Viewed by 4341

Abstract

In the past two decades, polarization gratings (PGs) have attracted intensive attention due to the high-efficient diffraction and polarization selectivity properties. On one hand, the one-dimensional (1D) PGs have been investigated widely and adapted to various applications. On the other hand, optical signal [...] Read more.

In the past two decades, polarization gratings (PGs) have attracted intensive attention due to the high-efficient diffraction and polarization selectivity properties. On one hand, the one-dimensional (1D) PGs have been investigated widely and adapted to various applications. On the other hand, optical signal manipulation stimulates the development of multibeam optical devices. Therefore, the development of two-dimensional (2D) PGs is in demand. This review summarizes the research progress of 2D PGs. Different designs and fabrication methods are summarized, including assembling two 1D polarization patterns, a 2D holographic lithography by polarization interference and a micro-pixelated electric field stimulated 2D liquid crystal (LC) structure. Both experiments and analyses are included. The design strategy, diffraction property, merits and demerits are discussed and summarized for the different methods. Full article

(This article belongs to the Special Issue Liquid Crystals in China)

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