Abstract
We report calculations of phonon dispersions of iron (Fe) at its phase transition using a self-consistent ab initio lattice dynamical method in conjunction with an effective magnetic force approach via the antiferromagnetic approximation. Our results show that anharmonic phonon-phonon interactions play a crucial role in stabilizing the -Fe phase in the open bcc lattice. In contrast, the lattice dynamics of the close-packed fcc -Fe phase are dominated by magnetic interactions. Simultaneous considerations of the lattice anharmonic and magnetic interactions produced temperature-dependent phonon dispersions for -Fe and -Fe phases in excellent agreement with recent experimental measurements. The present results highlight the key role of lattice anharmonicity in determining the structural stability of iron at high temperatures, which has significant implications for other high-temperature paramagnetic metals like Ce and Pu.
- Received 23 June 2015
- Revised 30 October 2015
DOI:https://doi.org/10.1103/PhysRevB.92.184110
©2015 American Physical Society