Corrected effective medium method. I. One-body formulation with applications to atomic chemisorption and diatomic molecular potentials

Abstract

We have derived a corrected effective medium (CEM) theory which describes the binding between an atom and an inhomogeneous host. As in all EM theories, the zeroth order term of the interaction energy is provided by the embedding energy of the atom into a spin-unpolarized homogeneous electron gas, and is obtained from self-consistent calculations within the local density approximation. Higher order terms provide corrections of two sorts: (1) the Coulomb interaction is accounted for by an explicit evaluation of the electrostatic interaction between the atom charge density and the host charge density; and (2) the difference in kinetic, exchange, and correlation energies between the atom/inhomogeneous system and the atom/homogeneous system is provided by a spin-polarized density functional evaluation. Both the Coulomb and difference energies are calculated non-self-consistently within the superposition of atomic densities approximation. A sampling procedure to obtain the homogeneous electron density from the inhomogeneous host density is derived by minimization of the contributions from the non-self-consistent difference term. Applications of the CEM theory are made to three types of systems that reflect a measure of difference in the spin polarization and inhomogeneity of both the atom and host spin density. We first describe the interaction of an H atom embedded into a spin-polarized homogeneous electron gas. Next, we calculate the binding potentials for a set of diatomic hydrides. Finally, we predict the interaction potentials for the chemisorption of H atoms on three different transition metal surfaces, Ni(100), Cu(100), and Fe(110).