Structural, electronic and optical properties of KTa_0.5Nb _0.5O₃ surface: A first-principles study

The crystal surface properties of potassium tantalite niobate, KTa _0.5Nb_0.5O₃ (KTN), are studied with first-principles calculation based on the density functional theory (DFT). Generalized gradient approximation (GGA) functional analysis is also employed by using CASTEP software. The explanations for the differences of the ferroelectric and piezoelectric properties between the bulk and surface of the material are provided. The DFT with GGA is used to determine the structure and to calculate the electronic and optical properties of the chemically ordered KTa_0.5Nb_0.5O₃ crystal (100), (110) and (111) surfaces. The results show that the surface properties are different from the bulk properties. The data obtained agree with the expected values and can serve as guidance for future experimental studies in the fields of photorefraction and nonlinear optics.