Special Issue "Compounds with Polar Metallic Bonding"
Deadline for manuscript submissions: 31 October 2018
Dr. Constantin Hoch
This Special Issue on “Compounds with Polar Metallic Bonding” is intended to open an exchange between chemical, physical and material-oriented disciplines committed to intermetallic systems with strongly correlated electrons. The term “polar metal” is ubiquitous here, and can describe numerous different effects. Polarity can indicate the interplay of conduction electrons with magnetic dipoles in the lattice. It can also describe the presence of electric dipole moments within a ferroelectric metal. Additionally, the term is used when referring to an intermetallic phase crystallising in a polar space group, or when electronegativity differences between the constituent elements of an intermetallic phase induce Coulombic interactions within an overall metallic matrix.
In all these cases, polarity induces new, interesting property combinations in metallic systems. To understand the mechanisms in this field, it is necessary to understand interplay between localised moments, as electric or magnetic dipoles, as well as Coulombic monopoles with the delocalized conduction electrons. For the establishment of structure–property relations for compounds with polar metallic bonding it is indispensable to present reliable models of their electronic structures. In order to understand the electronic consequences of polarity on the basis of quantum-mechanical calculations, it is necessary to have detailed crystal structure models at hand. Additionally, prior to crystal structure elucidation there is, of course, chemical synthesis.
We would like to combine reports on all related topics in this special issue. Some specifically interesting topics that may be included are listed below as keywords. These should only be considered as examples—any advanced topic in the field of polar metallic bonding is welcome.
Dr. Constantin Hoch
Manuscript Submission Information
Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.
Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.
Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.
- Synthesis of compounds with polar metallic bonding
- Crystal structure reports in polar intermetallics
- Band structure calculations and electronic structure modelling
- Physical properties and structure-property relations
- Bulk phases, thin films and cocrystals of polar intermetallic systems
- Polar metallic systems in applications
The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.
Title: Ammoniates of Zintl phases: Structural relations between intermetallic compounds A4E4 (A=Li-Cs, E=Si-Sn) and their corresponding ammoniate structures
Authors: Corinna Lorenz, Stefanie Gärtner, Nikolaus Korber
Abstract: The combination of electropositive alkali metals A (A=Na-Cs) and group 14 elements E (E= Si-Pb) in a stoichiometric ratio of 1 : 1 in solid state reactions results in the formation of polyanionic salts, which are commonly known as Zintl compounds. Crystal structure analysis of these intermetallic phases proved the presence of tetrahedral tetrelide tetraanions [E4]4− precast in solid state,[] and coulombic interactions account for the formation of a dense, three-dimensional cation-anion network. In addition, it has been shown that [E4]4− polyanions are also present in solutions of liquid ammonia prepared via different synthetic routes. From these solutions crystallize ammoniates of the alkali metal tetrahedranides, which contain ammonia molecules of crystallization and which can be characterized by X-ray crystallography despite their low thermal stability. The question to be answered is about the structural relations between the analogous compounds in solid state vs solvate structures, which all include the tetrahedral [E4]4− anions. We will investigate the similarities and differences regarding the coordination spheres of these anions as and the resulting cation - anion network. Specifically, we will include the reported solvates Na4Sn4·13NH3,[] Rb4Sn4·2NH3, Cs4Sn4·2NH3, Rb4Pb4·2NH3[] as well as the up to now unpublished crystal structures of the new compounds Cs4Si4·7NH3, Cs4Ge4·9NH3, [Li(NH3)4]4Sn4·4NH3, Na4Sn4·11.5NH3 and Cs4Pb4·5NH3 . Additionally, the influence of the presence of another anion on the overall crystal structure is discussed by using the example of a hydroxide co-crystal which was observed in the new compound K4Sn4(OH)0.5 ∙ 1.75 NH3
 E. Busmann, Z. Anorg. Allg. Chem.1961, 313, 90; H. G. v. Schnering, M. Schwarz, J.-H. Chang, K. Peters, E.-M. Peters, R. Nesper, Z.Kristallogr. New Cryst. Struct. 2005, 220, 525; T. Goebel, Y. Prots, F. Haarmann, Z. Kristallogr. New Cryst. Struct 2008, 223, 187; H. G. v. Schnering, J. Llanos, J.-H. Chang, K. Peters, E.-M. Peters, R. Nesper, Z. Kristallogr. New Cryst. Struct. 2005, 220, 324; J. Witte, H. G. v. Schnering, Z. Anorg. Allg. Chem. 1964, 327, 260; M. Baitinger, Y. Grin, R. Kniep, H. G. v. Schnering, Z. Kristallogr. 1999, 214, 457; M. Baitinger, K. Peters, M. Somer, W. Carillo-Cabrera, Y. Grin, R. Kniep, H. G. v. Schnering, Z. Kristallogr. 1999, 214, 455; R. Schäffer, W. Klemm, Z. Anorg. Allg. Chem. 1961, 312, 214; E. Hohmann, Z. Anorg. Allg. Chem. 1948, 257, 113; T. Goebel, A. Ormeci, O. Pecher, F. Haarmann, Z. Anorg. Allg. Chem. 2012, 638, 1437 – 1445; Grin, Y., Baitinger, M., Kniep, R., & Von Schnering, H. G. (1999). Z. Kristallogr-NCS 1999, 214(4), 453-454; Marsh, R. E., and D. P. Shoemaker, Acta Crystallogr. 1953, 6, 197-205; Hewaidy, I. F., Busmann, E., Klemm, W., Z. anorg. allg. Chem. 1964 , 328, 283–293
 M. Waibel, T. F. Fässler Z. Naturforsch. 2013, 68b, 732–734.
 K. Wiesler, K. Brandl, A. Fleischmann, N. Korber, Z. Anorg. Allg. Chem. 2009, 635, 508.
Title: Lu5Pd4Ge8 and Lu3Pd4Ge4: two more germanides among polar intermetallics
Authors: Riccardo Freccero 1, Pavlo Solokha 1, Davide M. Proserpio 2, 3, Adriana Saccone1, Serena De Negri 1
1 Università degli Studi di Genova, Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31, I-16146 Genova, Italy
2 Università degli Studi di Milano, Dipartimento di Chimica, Via Golgi 19, 20133 Milano, Italy
3 Samara Center for Theoretical Materials Science (SCTMS), Samara National Research University, Ac. Pavlov St 1, Samara 443011, Russia
Abstract: The two novel Lu5Pd4Ge8 and Lu3Pd4Ge4 polar intermetallics were prepared by direct synthesis of pure constituents. Their crystal structure was determined by single crystal X-ray diffraction analysis: Lu5Pd4Ge8 is monoclinic, P21/m, mP34, a = 5.7406(3), b = 13.7087(7), c = 8.3423(4) Å, b = 107.8(1), Z = 2; Lu3Pd4Ge4 is orthorhombic, Immm, oI22, a = 4.1368(3), b = 6.9192(5), c = 13.8229(9) Å, Z = 2. The Lu5Pd4Ge8 analyzed crystal is one more example of non-merohedral twinning among the rare earth containing germanides.
The crystal structure analysis of all known Ge-rich Lu-Pd-Ge compounds reveals a regular change of the type of Ge covalent fragments and their connection by means of Pd atoms, as a function of composition. The complexity of covalent Ge motifs increases along with Ge and Lu content evolving from Ge-Ge dumbbells to chains and from cis-Ge4 units to infinite corrugated 3-bonded layers.
Electronic structure calculations on the title compounds confirm the role of Lu in stabilization of Ge covalent fragments. The type/energy of the different interactions were evaluated in the framework of the projected COHP method.
Title: Crystal Structure, Spectroscopic Investigations and Physical Properties of the Ternary Intermetallic REPt2Al3 (RE = Y, Dy–Tm) and RE2Pt3Al4 Representatives (RE = Tm, Lu)
Authors: Oliver Janka et al.
Abstract: The /RE/Pt_2 Al_3 compounds of the late rare-earth metals (/RE/ = Y, Dy–Tm) were found to crystallize isostructural. Single crystal X-ray investigations of YPt_2 Al_3 revealed an orthorhombic unit cell (/a/ = 1080.73(6), /b/ = 1871.96(9), /c/ = 413.04(2) pm, /wR/2 = 0.0780, 942 F^2 values, 46 variables) with space group /Cmmm/ (/oC/48; /q/^2 /pji/^2 /hedb/). Comparison with the Pearson database indicated that YPt_2 Al_3 forms a new structure type, in which the Pt and Al atoms from a [Pt_2 Al_3 ]/^δ /^–polyanion, the Y atoms reside in cavities within the framework. Via a group-subgroup scheme, the relationship between the PrNi_2 Al_3 type structure and the new YPt_2 Al_3 type was illustrated. The compounds with /RE/ = Dy–Tm were characterized by powder X-ray diffraction experiments. While YPt_2 Al_3 is a Pauli-paramagnet, the other /RE/Pt_2 Al_3 (/RE/ = Dy–Tm) compounds exhibit paramagnetic behavior, in line with the rare-earth atoms being in the trivalent oxidation state. Attempts to synthesize the isostructural lutetium compound resulted in the formation of Lu_2 Pt_3 Al_4 (Ce_2 Ir_3 Sb_4 type, /Pnma/, /a/ = 1343.4(2), /b/ = 416.41(8), /c/ = 1141.1(2) pm). The structure was refined from single crystal data (/wR/2 = 0.0940, 1605 F^2 values, 56 variables). Again a polyanion with bonding Pt–Al interactions is found, the two distinct Lu atoms reside in cavities of the [Pt_3 Al_4 ]/^δ /^– framework. XPS measurements were conducted to examine the electron transfer from the rare-earth atoms onto the polyanionic framework.