Stability of the hcp phase and temperature variation of the axial ratio of iron near Earth-core conditions

Abstract

We theoretically document the stability of hcp iron for pressure–temperature conditions of the Earth’s inner core by separately computing the electronic and phonon contributions to the free energy. These pseudopotential-based quasi-harmonic calculations reveal that the hcp phase remains stable compared to bcc and that the c/a ratio of lattice parameters exhibits only a modest temperature dependence at inner-core conditions.