First principles calculation of finite temperature magnetism in Fe and Fe 3 C

• Published in: Journal of applied physics Vol. 109; no. 7; pp. 07E138 - 07E138-3
• Main Authors: Eisenbach, M., Nicholson, D. M., Rusanu, A., Brown, G.
• Format: Journal Article
• Language: English
• Published: United States American Institute of Physics 05.04.2011; American Institute of Physics (AIP)
• Subjects: nuclear (including radiation effects), defects, mechanical behavior, spin dynamics, materials and chemistry by design
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.3562218

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 systems 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, Phys. Rev. Lett. 86 , 2050 (2001)] with our first principles multiple scattering electronic structure code [Y. Wang , Phys. Rev. Lett. 75 , 2867 (1995)] that allows the energy calculation of constrained magnetic states [M. Eisenbach , Proceedings of the Conference on High Performance Computing, Networking, Storage and Analysis (ACM, New York, 2009)]. We present our calculations of finite temperature properties of Fe and Fe 3 C using this approach and we find the Curie temperatures to be 980 and 425K, respectively.