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

The dependence of the direct gap of germanium (Γ25'{→}Γ2') 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 dE₀/dp obtained for the gap is very well reproduced. The dependence of E₀ on the relative change of lattice constant ({Δ}scra/scra₀) is shown to be supralinear.