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Structure, bonding and physical properties of tetragonal and orthorhombic SiS2 from (hybrid) DFT calculations |
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| Authors: | Martijn A Zwijnenburg Robert G Bell Furio Corà |
| Institution: | a Davy Faraday Research Laboratory, University College London, Gower Street, Kathleen Lonsdale Building, 3rd Floor, London WC1E 6BT, UK b Christopher Ingold Laboratories, Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, UK c Materials Simulation Laboratory, University College London, Gower Street, London WC1E 6BT, UK |
| Abstract: | The energetics, structure and physical properties of tetragonal and orthorhombic SiS2 were calculated by periodic density functional theory (DFT) calculations, using both localized orbital and projected augmented wave basis-sets. All methods applied agree upon the relative energies of the different polymorphs but show differences in the predicted geometries, which are minimized upon improving the basis-set quality. The hybrid PBE0 functional was found to give the best match between experimental and calculated structures. When comparing SiS2 with its much better studied oxide analog silica, we observe that upon substituting sulphur for oxygen, the energy landscape changes dramatically. Other effects of changing S for O are found to be smaller Si-X-Si angles, a broader distribution of X-Si-X angles, a more flexible framework and a significantly reduced band gap. The latter is in line with the experimental observation of photoluminescence in related GaGeS2 compounds and suggests that SiS2 might find application in UV light emitting diodes. Finally, a comparison of the maximally localized Wannier functions demonstrates that the Si-S bonds in SiS2 have a considerably more covalent character than the Si-O bonds in silica. |
| Keywords: | Silicon sulphide Chalcogenide Silica DFT |
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