Mechanical properties, hardness and electronic structures of new post-cotunnite phase (Fe2P-type) of TiO2

Based on the first-principles calculations, we investigate mechanical properties, hardness and electronic structures of the new Fe2P-type TiO2. The computed equilibrium lattice constants and mechanical moduli of Cotunnite-TiO2 are in agreement with those experimental values and previous calculated data. The mechanical moduli (bulk, shear and Young's moduli) are evaluated by Voigt-Reuss-Hill approach. We plot the planar contours of bulk and Young's moduli of Fe2P-TiO2 structure at several crystallographic planes ((0 0 1) and (1 0 0)) to reveal their anisotropy in elasticity. The Šimůnek's method is applied to calculate the Vickers hardness of Fe2P-type of TiO2. Moreover, Fe2P-TiO2 shows strong ionicity from the computed angular momentum projected density of states. The computed hardness of Fe2P-TiO2 is below 20 GPa.