First principle study on electronic structure, elastic properties and debye temperature of pure and doped KCaF3

As a potential functional material in the perovskite family, the electronic structure, elasticity, Debye temperature and anisotropy of pure and doped KCaF3 structures are investigated based on density functional theory (DFT). The virtual crystal approximation (VCA) and supercell doping methods are employed to study the relation between the dopant amount and band gap. Results show that: (1) The pure KCaF3 is an indirect band-gap semiconductor, with Young's modulus E of 64.20 GPa and band gap of 6.151 eV; (2) Band gap of doped KCaF3 after the supercell doping decreases to 4.900 eV, with the top of valence band and the bottom of conduction band changed while the doped KCaF3 becomes a direct band gap semiconductor; (3) Based on GGA and Reuss-Voigt-Hill methods, the E values of doped KCaF3 after VCA and supercell doping are 71.48 GPa and 84.02 GPa, respectively, demonstrating that the doped structure is stiffer than undoped structure. The bulk modulus to shear modulus ratio of pure KCaF3 seems to be relatively ductile, and the universal anisotropic index shows that both pure and doped KCaF3 exhibit fairly high elastic anisotropy. This research provides theoretical guidance for the design of new ABX(3)-type materials with better performance.