Theoretical investigation of structural, elastic, electronic, and thermal properties of KCaF3, K0.5Na0.5CaF3 and NaCaF3 Perovskites

• In this work we have studied the physical properties of KCaF3, NaCaF3 and K0.5Na0.5CaF3 Perovskites.
• The exchange–correlation energy is treated within GGA.
• The electronic structures show that these materials exhibit an indirect band gap.

All-electron self consistent Full Potential Augmented Plane Waves plus local orbital (FP-APW+lo) method within PBE and PBEsol Generalized Gradient density approximations are used to investigate structural, elastic, electronic and thermal properties of the cubic KCaF3, NaCaF3 and K0.5Na0.5CaF3 Perovskites. The calculated structural parameters such as equilibrium lattice constants, bulk moduli and their pressure derivatives are well consistent with the experimental and theoretical data. Using Mehl method, the elastic constants and their related parameters such as Young modulus, shear modulus and Poisson ratio are calculated for these materials. Electronic band structure investigation shows that LDA approximation within mBJ potential provides an enhancement band gap value of 55.49%, 43.64% and 47.81% respectively for KCaF3, NaCaF3 and K0.5Na0.5CaF3 compared to GGA-PBE. Therefore, these compounds exhibit clearly an indirect wide-gaps from R to Γ for both KCaF3, NaCaF3 and from M to Γ for K0.5Na0.5CaF3. Furthermore we have analyzed the thermodynamic properties by using the quasi-harmonic Debye model. We have also, predicted the dependent-temperature behavior of heat capacities and the volume of unit cell in wide range temperatures for these compounds.