Conceptual improvements of the KKR method

We review some recent conceptual improvements of the Korringa-Kohn-Rostoker (KKR) Green function method for electronic structure calculations. After an introduction into the KKR-Green function method we present an extension of this method into an accurate full-potential scheme, which allows calculation of forces and lattice relaxations. The additional numerical effort compared to the atomic sphere approximation scales only linear with the number of atoms. In addition, we discuss the recently developed screened KKR method which represents a reformulation of the multiple scattering theory with exponentially decreasing structure constants. This method, which has the same accuracy as the standard KKR method, exhibits strong advantages for two-dimensional systems like multilayers or surfaces, since the numerical effort scales linearly with the number of layers. The strength of both methods is illustrated in typical applications.