A new generalized Kohn-Sham method for fundamental band-gaps in solids

Abstract

We developed a method for calculating solid-state ground-state properties and fundamental band-gaps using a generalized Kohn-Sham approach combining a local density approximation (LDA) functional with a long-range explicit exchange orbital functional. We found that when the range parameter is selected according to the formula \gamma=A/(\eps_\inf - \eps_\tilde) where \eps_\inf is the optical dielectric constant of the solid and \eps_\tilde= 0.84 and A= 0.216a0^(-1), predictions of the fundamental band-gap close to the experimental values are obtained for a variety of solids of different types. For most solids the range parameter \gamma is small (i.e. explicit exchange is needed only at long distances) so the predicted values for lattice constants and bulk modulii are similar to those based on conventional LDA calculations.