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We present an application of a novel ab initio approach to calculate the total energy of materials with correlated electrons [1]. It combines band structure and dynamical mean-field theory, and is implemented in terms of plane-wave pseudopotentials. Here we employ this computational scheme to study the equilibrium crystal structure and phase stability of paramagnetic iron at the α(bcc)-γ(fcc) phase transition as a function of temperature [2]. For this purpose we analyzed the energetics of the bcc-fcc lattice transformation in Fe using the Bain transformation path. We find that at ambient pressure the temperature of the bcc-fcc structural phase transition occurs at ∼200 K above the calculated Curie temperature. The structural optimization performed for paramagnetic Fe yields the correct lattice constants and predicts a 2 % shrinking of the volume at the bcc-fcc phase transition. The magnetic correlation energy is found to be an essential driving force behind the bcc-fcc structural phase transition in paramagnetic iron. The phonon dispersion curves calculated for paramagnetic iron at the bcc-fcc structural phase transition show good agreement with experimental data.
[1] I. Leonov, N. Binggeli, Dm. Korotin, V. I. Anisimov, N. Stojic, and D. Vollhardt, Phys. Rev. Lett. 101, 096405 (2008); I. Leonov, Dm. Korotin, N. Binggeli, V. I. Anisimov, and D. Vollhardt, Phys. Rev. B 81, 075109 (2010). [2] I. Leonov, A. I. Poteryaev, V. I. Anisimov, and D. Vollhardt, arXiv:1008.4342 (2010). |
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