The exchange and correlation energy of a spin-polarised electron gas

Abstract

As a step in the calculation of gradient terms to the exchange and correlation energy in the spin-density functional theory, the authors consider the perturbation expansion of this energy for a paramagnetic electron gas. It is shown that the two relevant kernels can be expressed exactly in terms of the density and magnetisation dependence of the pair functions for the inhomogeneous gas. A method based upon the fitting of the third frequency moments of the density and spin-density response functions is used to calculate the perturbation kernels for a range of electron density. It is shown that the correlation contribution to these kernels can be substantial.