Electronic correlations determine the phase stability of iron up to the melting temperature

Abstract

We present theoretical results on the high-temperature phase stability and phonon spectra of paramagnetic bcc iron which explicitly take into account many-body effects. Several peculiarities, including a pronounced softening of the [110] transverse (T$_1$) mode and a dynamical instability of the bcc lattice in harmonic approximation are identified. We relate these features to the ${\alpha}$-to-${\gamma}$ and ${\gamma}$-to-${\delta}$ phase transformations in iron. The high-temperature bcc phase is found to be highly anharmonic and appears to be stabilized by the lattice entropy.