Mg partitioning between solid and liquid iron under the Earth’s core conditions

Recent studies show the Earth’s core may contain more magnesium (Mg) than previously thought, with perhaps up to 6 wt% in the early core and ∼1wt% still existing now. The Mg partitioning between liquid and solid iron (Fe) under the relevant conditions is needed, therefore, in order to establish whether the presence of magnesium will have an effect on core properties, particularly those of the inner core. Using the techniques of ab initio molecular dynamics (AIMD) and thermodynamic integration, we have calculated the chemical potential and partition coefficient of Mg between solid and liquid Fe at 360 GPa and 6500 K. We find Mg partitioning slightly favours liquid Fe but still allows a significant amount of Mg into the solid, which will likely make a small but important contribution to the light-element effects on core properties.