First−principles study: Structural, mechanical, electronic and thermodynamic properties of simple−cubic−perovskite (Ba0.62K0.38)(Bi0.92Mg0.08)O3

Abstract

A new simple cubic perovskite superconductor (Ba0.62K0.38)(Bi0.92Mg0.08)O3 with a Tcmag ∼30 K has been recently synthesized by utilizing facile hydrothermal conditions at 220 °C. Here, we have employed the pseudo-potential plane-wave (PP–PW) approach based on the density functional (DFT) theory, within the generalized gradient approximation (GGA) to calculate and investigate the physical and electronic properties of this new superconductor. The calculated elastic constants satisfy the Born mechanical stability criterion. Based on the calculated data of Cauchy pressure, Pugh ratio and Poisson's ratio, the compound under investigation is found to be brittle nature. The calculated Peierls stress indicates easier movement of dislocations between glide planes. The energy bands crossing the Fermi level (EF) in electronic band structure reveal metallic behavior of the newly synthesized compound. The contribution of O-2p orbital electrons at the EF is higher than those of other orbital electrons as seen from partial density of states. The formation of saddle point owing to the flatness of the energy band may enhance the electron pairing which subsequently leads to high-TC superconductivity. The valence electron charge density map shows the isotropic nature of charge distribution. Coexistence of electron and hole like pockets form the multi sheets Fermi surfaces and exhibit the multi-band nature of the compound. Importantly, Fermi surfaces with flat faces are considered as favorable condition for Fermi surface nesting. The calculated value of electron-phonon coupling constant (λ = 1.61) implies that the studied compound can be treated as a strongly coupled superconductor. Further, the thermodynamic properties at elevated temperature and pressure are calculated and analyzed for the first time by using quasi-harmonic model.