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Density functional calculations have proven to be a useful tool in the study of ground state properties of many materials. The investigation of finite temperature magnetism on the other hand has to rely usually on the usage of empirical models that allow the large number of evaluations of the system's Hamiltonian that are required to obtain the phase space sampling needed to obtain the free energy, specific heat, magnetization, susceptibility, and other quantities as function of temperature. We have demonstrated a solution to this problem that harnesses the computational power of today's large massively parallel computers by combining a classical Wang-Landau Monte-Carlo calculation [F. Wang and D. P. Landau, PRL 86, 2050 (2001)] with our first principles multiple scattering electronic structure code (LSMS) that allows the energy calculation of constrained magnetic states [M. Eisenbach et al., SC'09: Proceedings of the Conference on High Performance Computing, Networking, Storage and Analysis, ACM (2009)]. We present our method and our calculations of finite temperature properties of Fe and Fe3C using this approach and we find the Curie temperatures to be 980K and 400K respectively.
This research was performed at Oak Ridge National Lab under the auspices of the Division of Materials Science and Engineering, Office of Basic Energy Science of the US Department of Energy, managed by UT-Battelle, LLC, for the U. S. Department of Energy. This research used resources of the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory, which is supported by the Office of Science of the Department of Energy under contract DE-AC05-00OR22725. |
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