First Principles Calculation of Tetragonal (P4 mm) Pb-free Ferroelectric Oxide of SnTiO₃

Abstract

The properties of tetragonal (P4 mm, 99 space group) SnTiO3 were investigated via first-principles implemented in CASTEP computer code. The calculation of formation energy shows that the tetragonal P4 mm with the lowest energy optimization is at the ground state equilibrium structure compared to the ilmenite structure. The result also shows that SnTiO3 has a higher tetragonality (c/a = 1.18). Moreover, the elastic constant of SnTiO3 also confirmed that this compound has the tetragonal phase with a good mechanical stability. The electronic properties also indicated that the hybridizations occur among anion O 2p, cation Sn 5s and the Ti 3d states with an indirect band gap at the X-G point. The optical properties of SnTiO3 were determined by the complex dielectric constant and refractive index and they were compared to PbTiO3.