Structural, electronic, and optical properties of ferroelectric KTa1/2Nb1/2O3 solid solutions

Abstract

The first principles calculations within generalized gradient approximation have been used to determine the structural, electronic, and optical properties of three chemically ordered ferroelectric KTa 1 / 2 Nb 1 / 2 O 3 phases, with B site cations ordered along the [100], [110], and [111] directions. Stable ferroelectric ground states are found in all structures. The energy bands, density of states, complex dielectric function, reflectivity, refractive index, extinction coefficient, optical conductivity, absorption coefficient, and energy loss function are calculated by using the stable ferroelectric structures. The calculated results show good agreement with the available experimental and theoretical data. It is found that the ferroelectric states are particularly sensitive to the chemical ordering of B site cations and the long-range ordering has significant effect on the properties of KTa 1 / 2 Nb 1 / 2 O 3 crystals.