Phase transition and thermoelectric properties of cubic KNbO3 under pressure: DFT approach

In present study, the effect of pressure on the electronic, thermoelectric and optical properties of cubic KNbO3 compound is investigated using Predew-Burke-Ernzerhofgeneralized gradient approximation (PBE + GGA) in the framework of density functional theory. At 0 GPa, the calculated electronic band structure and density of states predict the indirect semiconducting nature of KNbO3, which is transformed into direct band gap at 180 GPa. Furthermore, the band gap decreases from 2.3 eV to 2 eV as the pressure upsurge from 0 GPa to 180 GPa. For optical characteristics, absorption and extinction coefficients, dielectric function, reflectivity, refractive index, and optical conductivity are calculated in the range of 0–10 eV at different pressures. Moreover, thermoelectric (TE) properties of the mention compound are investigated in terms of electrical conductivity, power factor, Seebeck coefficient, thermal conductivity using the Boltz-Trap code. The Seebeck coefficient decreases and electrical conductivity increases with the increase in pressure. Hence, KNbO3 is found to be a suitable compound for optoelectronic and thermoelectric applications.