Structural, electronic and optical properties of KTaO3 under high pressure based on first-principles

It is generally accepted that high pressure could bring out a inner change and atoms redistribution for KTaO3 (abbreviated as KT). As a result, the dielectricity, conductivity and optical properties of KT would be varied with the increase of pressure. In this paper, the structural, electronic and optical properties of KT under different pressures have been investigated based on the first-principles. When the pressure is below 60 GPa, the band gap of KT would be increased with the rise of pressure. However, when the pressure above 60 GPa, band gap show a sudden decrease. In order to the investigate the optical properties of KT, we calculated the function of dielectric function, refractive index, reflectivity and energy loss with frequency. With the increasing of pressure, the first peak in dielectric, refractive and reflective spectra exhibit a red shift. However, the other peaks show obvious blue shift. With increasing of pressure, the peak for energy loss function shift toward the higher energy. Moreover, in the visible region, the refractive index of KT shows a normal dispersion under high pressure. The controllable refractive index allows KT to be a promising material for optoelectronic device.