Density Functional Calculations of the Electronic Band Structure and Optical Properties of KCaF_3

The electronic band structure and optical properties of cubic KCaF_3 are studied using the density functional theory. The calculated band structure of cubic KCaF_3 shows an indirect band gap with two values of 5.95 eV and 5.94 eV at the M → Γ and Γ → R lines of Brillouin zone, respectively. The structural optimization has been performed using the generalized gradient approximation (GGA). The calculated structure optimization of KCaF3 has been compared with experimental results. Good agreement between theoretical and experimental results was observed. Moreover, some optical constants such as energy-loss functions for volume and surface, coefficients of extinction, reflectivity and absorption, refractive index and effective number of valence electrons per unit cell participating in the inter-band transitions and the linear photon-energy-dependent dielectric functions have been calculated.