A systematic computational study to understand the effect of metals (Mg,Ca, Sr) doping and external isotropic static pressure on phase stability,electronic band structure and optical properties of KNbO_3

摘要

The phase stability, electronic energy-band structure, and their impact on optical properties of KNbO_3 in tetragonal phase have been studied, using the ultra-soft pseudopotential method within the generalized gradient approximation for exchange and correlation, with metals (Mg, Ca, Sr) doping and external isotropic pressure (5GPa-50GPa). The band structure shows that the O-2p and Nb-4d orbital electrons play a vital role in the development of upper valence band and band gap energy almost increases linearly with doping, except Mg, and by increasing the pressure. Analysis of DOS describes ionic, K and NbO_3 and covalent, Nb and O, bonding. In order to understand the influence of doping and external pressure on optical properties of the KNbO_3, the dielectric function real and imaginary parts, absorption coefficient, reflectivity, refractive index, loss function and extinction coefficient were computed. Variations in optical spectra profiles were analysed and discussed with electronic band structure determination.