Melting curves and entropy of melting of iron under Earth’s core conditions

• We have investigated the melting curves of iron using three MD techniques firstly.
• Melting points of Fe at Earth’s core conditions have been predicted successfully.
• Our melting equation could assess T distribution inside the Earth’s deep interior.
• The interfacial energy of Fe at Earth’s core conditions has been described firstly.

The melting curves of iron are determined up to 365 GPa via molecular dynamic (MD) simulations combining with the embedded atom model (EAM) potential developed by Ackland et al. We simulated the melting with three approaches, the hysteresis, two-phase and recently modified Z methods. All three techniques can produce satisfying results, consistent well with most of static compression measurements and shock experiments. Hence, we recommend that these three techniques and this EAM potential are reliable techniques and potential for simulating melting properties of iron. Fitting the well-known Simon equation to our two-phase data we yield the analytical melting curve for iron: 1825(1 + P/57.723)0.654, which gives a melting point at the inner core boundary of 6345 K, very close to the recent diamond anvil cell (DAC) extrapolated value and other ab initio calculations. Furthermore, the analyses of our entropy of melting and solid–liquid interfacial energy γsl indicate that at high pressure, the entropy of fusion shows weak pressure effect. The γsl increases monotonically with pressure, and can be described as a second-order polynomial relation.