Free energy of bcc iron: Integrated ab initio derivation of vibrational, electronic, and magnetic contributions
F. Körmann, A. Dick, B. Grabowski, B. Hallstedt, T. Hickel, J. Neugebauer.
Physical Review B, 78, 033102, (2008)
We present ab initio derived thermodynamic properties of ferromagnetic bcc iron up to the bcc-fcc phase-transition temperature (1200 K), including vibrational, electronic, and magnetic contributions. The quasiharmonic approximation and finite-temperature density-functional theory are employed to account for vibrational and electronic excitations. The magnetic contribution is derived from the solution of the quantum Heisenberg model within many-body theory using the mean-field and random-phase approximation. The calculated thermodynamic properties show an excellent agreement with available experimental data and reveal the necessity to consider all three types of excitations.
Keyword(s): finite-temperature; excitations; systems