Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 20: Electronic Properties II

MM 20.1: Vortrag

Dienstag, 26. Februar 2008, 10:15–10:30, H 0111

Non local exchange and correlations in Fe — •Gernot Stollhoff — MPI f. Festkörperforschung, Heisenbergstr.1, D 70569 Stuttgart

Density functional (DF) calculations obtain the correct ferromagnetic ground state of Fe. We had in the past demonstrated with the help of correlation calculations on 5 band Hubbard Hamiltonians that this is in part due to a chance compensation of big errors in the handling of local interactions. DMFT-calculations on similar models have shown that the biggest apparent DF-deficiency, the computed transition temperature, can be only partially improved, namely from 3500K to 2000K.

Recent ab-initio correlation calculations by the Local Ansatz falsify the underlying rigid band hypothesis in both approaches. While the non magnetic DF-results are the appropriate basis for the magnetic ground state, they fail for the non magnetic state itself. Here, not fully screened non local exchange contributions play a big role. The exact charge distribution is different, and the density of state is strongly modified, with n(EF) less than half the one of the DF-case. This causes an electronic first order phase transition. Also the resulting energy-bands differ. In contrast to the DF-results, these explain temperature dependent angular resolved photoemission experiments (Kirschner et al., PRL 53, 612 (1984)).