First-principles determination of the sublinear dependence of the direct &) on hydrostatic pressure

Abstract

The dependence of the direct gap of germanium (${\ensuremath{\Gamma}}_{25\mathcal{'}}$\ensuremath{\rightarrow}${\ensuremath{\Gamma}}_{2\mathcal{'}}$) on hydrostatic pressure has been calculated from first principles within local-density-functional formalism. This dependence is found to be sublinear. Although the correct gap cannot be obtained within the local-density-functional formalism its pressure dependence is still well accounted for. The linear pressure coefficient ${\mathrm{dE}}_{0}$/dp obtained for the gap is very well reproduced. The dependence of ${E}_{0}$ on the relative change of lattice constant (\ensuremath{\Delta}scra/${\mathrm{scra}}_{0}$) is shown to be supralinear.