The full potential Korringa-Kohn-Rostoker method and its application in electric field gradient calculations.

We have developed a full potential Korringa-Kohn-Rostoker (KKR) Green function method. Three improvements which make the full potential treatment efficient and practical are reported. One is a method for constructing the Green function which satisfies the Wronskian relation exactly. The second is including the contribution of the non-spherical part of the potential in the wavefunctions correctly by use of a modified recursive integral equation. Thirdly, we propose a method that completely eliminates the contribution of irregular solutions of the Schrödinger equation to charge/spin densities. In order to check the reliability of the method, we calculated the electric field gradient (EFG), which is sensitive to how the potential is treated. We have performed EFG calculations for hcp metals and sp impurities in Zn and Cd with the present method. The results are in good agreement with experimental data and show that the full potential KKR method is reliable enough for EFG calculations.