Berlin 2008 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 20: Electronic Properties II
MM 20.5: Talk
Tuesday, February 26, 2008, 11:15–11:30, H 0111
Does magnesium-like zinc in a nearly ideal hcp form exist? — Nicola Gaston1, •Beate Paulus2, Ulrich Wedig3, and Martin Jansen3 — 1Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Str. 38, 01187 Dresden — 2Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin — 3Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart
Zinc crystallises in the hcp structure, but with an anomalously large c/a ratio, indicating a strong distortion away from ideal packing. Density functional calculations of zinc fail to describe the unusual hcp structure of this material [1]. We perform a wavefunction-based correlation treatment on top of periodic Hartree-Fock calculations. This treatment corresponds to a many-body expansion of the correlation energy of the extended system in terms of localized orbital groups (method of increments)[2]. The Hartree-Fock treatment yields no binding and no equilibrium geometry for zinc. The binding of the ground-state structure is fully described by electronic correlations. Our values of the cohesive energy agree within 5% with the experimental value and within 2% for the lattice parameters. These calculations indicate additionally a local miminum of the potential energy surface for a c/a ratio which is almost ideally close-packed as in magnesium.
[1] B. Paulus, K. Rosciszewski, P. Sony, U. Wedig and M. Jansen Phys. Rev. B 75, 205123 (2007).
[2] N. Gaston and B. Paulus, Phys. Rev. B in press (2007)