Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 25: Phase Transitions
O 25.1: Vortrag
Dienstag, 27. März 2007, 11:15–11:30, H41
Order-disorder phase transitions: a DFT - (Wang-Landau) MC study — •Mira Todorova1, Mikael Borg2, Catherine Stampfl3, and Matthias Scheffler4 — 1Max-Planck Institut für Eisenforschung, Max-Planck-Str. 1, 40237 Düsseldorf — 2University of Toronto, Toronto, Canada — 3School of Physics, The University of Sydney, Australia — 4Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin
Using a hybrid statistical mechanics method comprising the use of a Lattice-gas Hamiltonian (LGH) determined from density-functional theory and subsequent Monte Carlo (MC) calculations, we obtain a phase diagram for Na-Al surface alloys from first-principles and compare it to experimental results [1].
A safe approach towards parametrizing a LGH from the self-consistent evaluation of the electronic structure starts with an analytic form for the long-range pair-interactions. This expression is corrected in the short and medium range using DFT derived data, also including nearsighted many-body terms. An ensuing cross-validation is of utmost importance to ensure that the corrections (to the long-range part) are assessed with an optimum accuracy. The thus extracted LGH is used to perform MC calculations, also using the new Wang-Landau MC algorithm [2], which allows us to reliably determine the transition temperature.
[1] M. Borg, et al., Chem. Phys.Chem. 6, 1923 (2005).
[2] F. Wang and D.P. Landau, Phys. Rev. Lett. 86, 2050 (2001).