Speaker
Prof.
Rudolf ZELLER
Description
Similar to the historical Wigner-Seitz (cellular) method for the solution of the Schroedinger equation in solids, the all-electron full-potential Korringa-Kohn-Rostoker (KKR) Green function (GF) method uses a partitioning of space into atomic (Wigner-Seitz) cells. However, instead of wave-function matching at the cell boundaries, the KKR-GF method is based on the direct solution of integral equations where the integral kernel is given as the product of the Green function of suitably chosen reference system and the electronic potential difference between the system of interest and the reference system.
In my talk I will show how a repulsive reference system and the complex-energy charge-density integration method can be exploited to achieve density-functional calculations with a computational effort that increases only linearly with N, the number of atoms in the system, thus avoiding the computational bottleneck of standard density-functional calculations where the effort increases with the third power of N. I will demonstrate that our newly developed code can be applied to systems with thousands of atoms and that it achieves a high computational efficiency even if many thousand computing cores are used.
I will also present two recent numerical advances concerning the accuracy of KKR-GF calculations. I will show how density-functional total energies can be obtained with computational errors smaller than tenths of millielectron-volts per atom and how accurate charge densities can be determined even in close vicinity to the nuclear sites by a novel numerical technique for the irregular coupled radial scattering solutions that are necessary to guarantee the correct analytical Green function behaviour in the complex energy plane.
