The effect of B site cations on the properties of para-electric KTa1/2Nb1/2O3 crystal from first-principles calculations

Density functional theory was used to investigate the effect of B site cations on the electric structures and optical properties of para-electric solid solution KTa1/2Nb1/2O3 (KTN) crystal. Three possible arrangements of B site cations (Mode A, Mode B, and Mode C) were presented. The geometry optimization was performed and stable para-electric ground states were obtained for three modes. The optimized lattice parameters are in good agreement with the experimental values. The density of states (DOS) and imaginary parts of dielectric function together with absorption coefficient are determined. The partial DOS of the B site cations are also different for three modes. It is found that KTN has anisotropic optical responses in Mode A and Mode B, and isotropic optical responses in Mode C. Therefore the B site cations influence the properties of KTN obviously.