First principles electronic and elastic properties of fresnoite Ba2TiSi2O8

Ned Taylor, Frank Davies, and Steve Hepplestone published an article detailing a theoretical study of the electronic and elastic properties of fresnoite, Ba2TiSi2O8. The work was performed during the first six months of Ned and Frank’s PhDs. This material has potential due to its large band gap, strongly anisotropic structure and a second gap directly above the band gap.

Using PBE density functional theory (DFT), the electronic and elastic properties are determined for defect-free fresnoite. To more accurately capture the band structure and band gap, results are also reported using the hybrid functional, HSE06.

Electronic properties such as the Bader charge, band structure, density of states, species- and atom-projected density of states are presented here (obtained and presented using both PBE and HSE06). The electronic contributions to the static and high-frequency permittivities along X and Z are also presented (obtained using PBE). The dielectric properties of fresnoite are of interest as it is known to form between layers of BaTiO3 and Si (or SiO2), a composite structure that is known to exhibit unusually high permittivity values (~104), even for BaTiO3. However, in this study, the authors show that fresnoite exhibits permittivity values only around 12.

Mechanical properties such as the bulk, shear and Young’s moduli are calculated. The elastic tensor values and the Raman-activated phonon frequencies are also presented. All mechanical properties are obtained using PBE.

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