Mechanically stiffened and thermally softened bulk modulus of BaXO3(X=Ti,Zr,Nb) cubic perovskites

Abstract

Although the physics behind the bulk modulus, B͑T , P͒, as a function of temperature ͑T͒ and pressure ͑P͒, has been intensively investigated, an atomic scale understanding of this attribute remains a high challenge. Here, we show that the B͑T , P͒ for BaXO 3 ͑X=Ti,Zr,Nb͒ can be established by connecting the B directly to the bond length and bond energy and their response to the applied T and P in the form of binding energy density, B͓E / d 3 ͑T , P͔͒. Besides an estimation of the Debye temperature and single bond energy, outcomes clarified that the thermally softened B arises from bond expansion and bond weakening due to lattice vibration and the mechanically stiffened B results from bond compression and bond strengthening due to mechanical work hardening.