High-pressure and temperature-induced structural, elastic, and thermodynamical properties of strontium chalcogenides

Pressure- and temperature-dependent mechanical,elastic, and thermodynamical properties of rock salt toCsCl structures in semiconducting SrX (X = O, S, Se, andTe) chalcogenides are presented based on model interatomicinteraction potential with emphasis on chargetransfer interactions, covalency effect, and zero pointenergy effects apart from long-range Coulomb, short-rangeoverlap repulsion extended and van der Waals interactions.The developed potential with non-central forces validatesthe Cauchy discrepancy among elastic constants. Thevolume collapse (V(P)/V(0)) in terms of compressions in SrX athigher pressure indicates the mechanical stiffening of lattice.The expansion of SrX lattice is inferred from steepincrease in V(T)/V(0) and is attributed to thermal softening ofSrX lattice. We also present the results for the temperaturedependentbehaviors of hardness, heat capacity, andthermal expansion coefficient. From the Pugh’s ratio(ϕ/ = B(T)/G(H)), the Poisson’s ratio (ν) and the Cauchy’spressure (C(12)–C(44)), we classify SrO as ductile but SrS,SrSe, and SrTe are brittle material. To our knowledge theseare the first quantitative theoretical prediction of the pressureand temperature dependence of mechanical stiffening,thermally softening, and brittle nature of SrX (X = O, S,Se, and Te) and still await experimental confirmations.