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

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.