Self-consistent Green-function method for the calculation of electronic properties of localized defects at surfaces and in the bulk

The authors 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.