Exchange-correlation correction to the dielectric function of the inhomogeneous electron gas

Abstract

Exchange-correlation (XC) and band structure corrections to the dielectric matrix are investigated simultaneously within the framework of non-local density functional theory. The XC correction is calculated in the weighted density approximation and band structure effects are taken into account in second order in the pseudopotential. Particular attention is devoted to the question of whether or not the minimum in the plasmon dispersion in caesium is connected with the hump in the static structure factor of the homogeneous electron gas near q=2kF, as concluded in a previous paper using frequency-momentum analysis. It was found that such a hump may lead to anomalies (in alkaline metals most probably minima) at those q that are solutions of the equation mod G-q mod =2kF, where G is any reciprocal lattice vector and kF is the Fermi momentum. In caesium, the location of the dominating minimum agrees with that of the experimental minimum, but its depth varies strongly for different homogeneous electron gas approximations.