Influence of phase transition on the mechanical and optical properties of SrSe and SrTe compounds via ab initio calculations.

Elastic and optical properties of strontium chalcogenides SrX (X = Se and Te) were studied under hydrostatic pressure using the flat wave method (PP-PW) implemented in the CASTEP code. The main parameter carried out was the pressure impact at ambient conditions. Indeed, under high pressures, both compounds have undergone a structural phase transition from B1 to B2 phases at ∼15.5 GPa and ∼12 GPa, respectively. Results also showed that in the B2 phase, the two postulated compounds have changed their electronic nature to become metals at metallic pressures equal to ∼16.8 GPa (SrSe) and ∼17.7 GPa (SrTe). Also, the elastic properties were calculated at different pressure values in NaCl and CsCl structures, including their elastic constants as a function of pressure for SrSe and SrTe. Their optical properties were also computed from the spectral data obtained through their dielectric function, refractive index (2.1, 2.3) and others in the visible range. [ABSTRACT FROM AUTHOR]