Characterization of the TiSiO4 structure and its pressure-induced phase transformations: density functional theory study

摘要

Theoretical investigations concerning the possible titanium silicate polymorphs have been performed usingdensity functional theory at B3LYP level. Total-energy calculations and geometry optimizations have beencarried out for all phases involved. The following sequence of pressure-driven structural transitions has beenfound: CrVO4-type, Cmcm in parenthesis the transition pressure , → zircon-type, I41/ amd 0.8 GPa , →scheelite-type, I41/ a 3.8 GPa . At higher pressure the last phase is found to be stable at least up to 25 GPa.The equation of state of the different polymorphs is also reported. We found that the highest bulk moduluscorresponds to the zircon and scheelite phases with values of 248 and 238 GPa, respectively. The orthorhombicCmcm phase is the most compressible of all the studied structures with a bulk modulus of 124 GPa, being alsothe most stable phase at ambient pressure. Finally, calculations of the electronic structure, vibrational anddielectric properties of TiSiO4are also reported