First principles investigation of electronic and elastic properties of strontium oxide and strontium peroxide phases: insights into structural stability and phase transitions

Abstract

Strontium oxide (SrO) and Strontium peroxide (SrO2) with multiple phases have been observed to exist at various temperatures and pressures, however there is little literature available on their properties. We have therefore attempted to discover several unexplored properties of various phases of SrO and SrO2. In this study, the electronic and elastic properties of SrO and SrO2 have been calculated via the first principle approach. We performed the said calculations over four available phases (FCC, BCC, hexagonal-1, and hexagonal-2) of SrO and two available phases (tetragonal and orthorhombic) of SrO2. The calculations have been conducted using density functional theory within the scalar-relativistic norm-conserving optimized Vanderbilt pseudopotential. In this study, equilibrium lattice parameter, elastic constants, structural stability, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, Pugh ratio, Universal anisotropy index, Cauchy pressure and Kleinman’s internal strain parameter as elastic properties; the band gap and nature of the band gap as electronic properties have been calculated for the aforementioned materials. The phase transition between FCC-SrO and BCC-SrO has been observed during the calculation of elastic properties at 47 GPa. Based on the mechanical stability criteria, all phases except SrO(BCC) and SrO(Hexagonal-2) have been found to pass. The value of the bulk modulus have been observed between 68 GPa and 88 GPa for the different phases of SrOx [x = 1, 2]. Satisfactory agreement could be found between the present results and the available theoretical and experimental results.