Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3
Abstract
:1. Introduction
2. Computational Methods and Models
2.1. Computational Methods
2.2. Computational Models
3. Results and Discussion
3.1. Structural Changes of Ag- and S-Doped α-Fe2O3
3.2. Electronic Structures of Pure, Ag- Doped and S-Doped α-Fe2O3
3.3. Optical Property of Pure, Ag-Doped and S-Doped α-Fe2O3
4. Conclusions
- (1)
- The doping of Ag and S results in a large change of the crystal structure of α-Fe2O3. The lengths of all Ag-O and S-Fe bonds are larger than those of corresponding O-Fe bonds before Ag and S doping, which induces the expansion of the α-Fe2O3 crystal.
- (2)
- The band gaps of α-Fe2O3 decrease after Ag and S doping. For Ag/α-Fe2O3, the energy levels near the Fermi level for the upspin and downspin bands are split and form small DOS peaks, respectively. The main contribution of Ag in the conduction band is from Ag 5p and Ag 5s orbitals and from Ag 4d orbital in the valence band. For S/α-Fe2O3, the energy levels near the Fermi level for the upspin and downspin bands are also split; however, two DOS peaks are formed, respectively. The main contribution of S is from S 3p with a few contributions of S 3s.
- (3)
- The absorption peaks of Ag-doped and S-doped α-Fe2O3 shift slightly to a short wavelength accompanying the increased peak intensity of S/α-Fe2O3 and decreased peak intensity of Ag/α-Fe2O3. When the wavelength is greater than 380 nm, the optical absorptions of Ag- and S-doped α-Fe2O3 in the visible range are stronger than that of pure α-Fe2O3, and the optical absorption of S-doped α-Fe2O3 is stronger than that of Ag-doped α-Fe2O3.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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k-Point | System Energy (103eV) | Lattice Parameters (Å) | |
---|---|---|---|
a (b) | c | ||
1 × 1 × 1 | −73.64 | 5.099 | 14.156 |
2 × 2 × 1 | −73.74 | 5.094 | 14.145 |
2 × 2 × 2 | −73.82 | 5.090 | 14.140 |
3 × 3 × 1 | −73.86 | 5.088 | 14.138 |
3 × 3 × 2 | −73.87 | 5.087 | 14.138 |
Computational Functions | System Energy (103·eV) | Lattice Parameters (Å) | |
---|---|---|---|
a (b) | c | ||
GGA-PBE | −72.23 | 5.0886 | 14.449 |
GGA-RPBE | −72.84 | 5.0901 | 14.248 |
GGA-PW91 | −73.86 | 5.0875 | 14.138 |
GGA-WC | −73.09 | 5.0879 | 14.219 |
Convergence Tolerance Parameters | Tolerances |
---|---|
Maximum energy change | 2.0 × 10−5 eV·atom−1 |
Maximum force | 0.05 eV·Å−1 |
Maximum stress | 0.1 GPa |
Maximum displacement | 0.002 Å |
Self-consistent field (SCF) | 2.0 × 10−6 eV·atom−1 |
Species | Atoms | Charge/e |
---|---|---|
Pure α-Fe2O3 | O | −0.760 |
O1 | −0.760 | |
O2 | −0.760 | |
O3 | −0.760 | |
O4 | −0.760 | |
O5 | −0.760 | |
Fe1 | 1.140 | |
Fe2 | 1.140 | |
Fe3 | 1.140 | |
Fe4 | 1.140 | |
Ag-doped α-Fe2O3 | Ag | 1.730 |
O | −0.690 | |
O1 | −0.720 | |
O2 | −0.740 | |
O3 | −0.720 | |
O4 | −0.680 | |
O5 | −0.690 | |
S-doped α-Fe2O3 | S | −0.230 |
Fe | 0.870 | |
Fe1 | 0.860 | |
Fe2 | 0.910 | |
Fe3 | 0.910 |
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Zhao, C.; Li, B.; Zhou, X.; Chen, J.; Tang, H. Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3. Metals 2021, 11, 424. https://doi.org/10.3390/met11030424
Zhao C, Li B, Zhou X, Chen J, Tang H. Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3. Metals. 2021; 11(3):424. https://doi.org/10.3390/met11030424
Chicago/Turabian StyleZhao, Cuihua, Baishi Li, Xi Zhou, Jianhua Chen, and Hongqun Tang. 2021. "Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3" Metals 11, no. 3: 424. https://doi.org/10.3390/met11030424