Study of the hydrostatic pressure on orthorhombic IV–VI compounds including many-body effects

We performed a fully ab initio study of the relaxed volume optimization of the four orthorhombic IV–VI compounds (GeS, GeSe, α-SnS and SnSe), finding good agreement with experimental data from the literature. Based on the framework of the density functional theory and with a pseudopotential approach, we constructed the quasiparticle GW scheme to adjust the band structure and densities of states of the systems at different pressures, discussing the trends of the band gaps, that show metallization. Also, and within an effective two-particle equation for the response function, which includes the electron–hole interaction effects, we included the GW and the effective electron–hole contributions to the real and imaginary parts of the dielectric function and to the absorption coefficient of the four compounds both, at ambient and higher pressures. Comparison with experiments shows a satisfactory degree of agreement.