SELF-CONSISTENT GREEN-FUNCTION METHOD FOR THE CALCULATION OF ELECTRONIC-PROPERTIES OF LOCALIZED DEFECTS AT SURFACES AND IN THE BULK

We present a self-consistent Green-function method which enables parameter-free calculations of the charge density, the density of states, and related quantities in electronic systems where the three- or two-dimensional translational symmetry is broken by a perturbation which is localized in real space. In particular, the method is suited to study point defects in the interior of a metallic or semiconducting crystal or at a crystal surface. The self-consistent Green operator describes an infinitely extended system. The only restrictive assumption is that the self-consistent electronic structure of the unperturbed bulk material is well reproduced by a muffin-tin (pseudo) potential. In the perturbed region, however, no significant constraint is imposed either on the shape of the potential or on the charge density. While the basic ideas of our method have been published elsewhere [1], in this paper the practical aspects will be discussed. The numerical practicality and efficiency of a first implementation based on a Gaussian basis set is illustrated with reference to selected test calculations.