Comparative study of cubic Pm3m between SnZrO3 and PbZrO3 by first principles calculation

The properties of perovskite SnZrO₃ (SZ) in cubic (Pm3m space group) was investigated via first principles calculation using the density functional theory (DFT) as implemented in CASTEP computer code. The lattice parameter of PbZrO₃ (PZ) was calculated as a reference compound and the results show an accuracy values relative to the experimental values. In this first-principle calculations, the exchange-correlation functional is based on LDA-CAPZ which give underestimate in structural lattice parameters with typical errors of 2%. The elastic constants and their pressure dependence were calculated up to 30 GPa, and independent elastic constants (C₁₁, C₁₂, and C₄₄), bulk modules, B are obtained and analyzed. Density of state (DOS) studies reveal that the anion O 2p, cation Sn 5p/Pb 5p and Zr 4d states of SZ and PZ play an important role which correspond to the top of valence states and bottom of conduction band. Meanwhile, direct band gap at X-X point is respectively obtained for both SZ and PZ along the higher symmetry direction in the Brillouin zone. The born effective charges (BEC) values of Sn and Zr (in SZ) have respectively been found to be +4.26 and +7.53. This is attributed to the bond charge response to the displacement caused by the strong covalency between cation orbital and O 2p. Results reveal anion O 2p, cation Sn 5p and Zr 4d states have also played an important role in optical transition in which they respectively correspond to the top of valence states and bottom of conduction band. The results of prototype SZ were compared and showed in good agreement with the calculated results of PZ.