Elastic, mechanical and thermodynamic properties of technetium-based perovskites XTcO3 (X = K, Rb) compounds

Abstract

Ab-initio calculations are employed to determine the structural, mechanical, elastic, electronic and thermodynamic properties of perovskite oxides XTcO3 (X = K, Rb). From the computed structural properties, KTcO3 and RbTcO3 are found to be stable with equilibrium lattice constants; 7.3943 Bohr and 7.4909 Bohr, respectively. From electronic structure results, a metallic character is remarked for both compounds. The determined elastic constants (C11, C12, C44) have indicated the mechanical stability of XTcO3 (X = K, Rb) compounds that is confirmed by the phonon spectra. In addition, KTcO3 is found to be isotropic and KTcO3 is nearly isotropic according the anisotropic constant A values. B/G ratio has indicated the brittleness of both compounds. Furthermore, the Helmholtz free energy (F), entropy (S) and heat capacity (CV) are determined using QHA (Quasi harmonic Approximation). Our computational indicates that XTcO3 (X = K, Rb) compounds can be used as new materials for solid oxide fuel cells and related applications.