The effect of non-orthogonality in the study of adsorption: Hydrogen on graphite

The effect of non-orthogonality between the localized orbitals of an adsorbed atom (or impurity atom) and those of the surrounding atoms of the substrate solid has been studied. The overlap matrix S takes in this case a simple form which enables us to calculate local densities of states and other local effects such as charges on the atoms by the continued fraction expansion. The method has been applied to a simplified model for the adsorption of hydrogen on graphite, and the results show an improvement with respect to calculations where the overlap is neglected.