Physics of the Earth and Planetary Interiors Ab Initio Lattice Dynamics Calculations on the Combined Effect of Temperature and Silicon on the Stability of Different Iron Phases in the Earth's Inner Core

The Earth’s solid inner core consists mainly of iron (Fe), alloyed with lighter elements, such as silicon (Si). Interpretation of seismic anisotropy and layering requires knowledge of the stable crystal structure in the inner core. We report ab initio density functional theory calculations on the free energy and vibrational stability of pure iron and Fe–Si alloys at conditions representative of the Earth’s inner core. For pure Fe the