IMPURITY CALCULATIONS VIA A DISTORTED-WAVE MATRIX GREEN-FUNCTION METHOD

The computational efficiency of matrix Green's-function scattering theory is improved by solving Dyson's equation in two steps. The first step yields a distorted-wave Green's function that incorporates the effects of the kinetic-energy matrix's impurity-host blocks. This is the longest-ranged component of the impurity-host interaction, but is iteration independent. The second step, which must be performed numerous times as one iterates to self-consistency, adds the effects of the electron-electron interaction. Computational effort per iteration is reduced because the range of the electron-electron interaction matrix is limited by screening. The distorted-wave method is illustrated via calculations of the adsorption energy of a single Al adatom on an Al(111) substrate.