First‐Principles Study of Thermodynamics and Spin Transition in FeSiO 3 Liquid at High Pressure

The thermodynamic properties of iron silicate liquids at high pressures and temperatures are poorly constrained, even though they are important for understanding the thermal and chemical evolution of a magma ocean. Here we report the results of the P‐V‐T equation of state, thermodynamic properties, and spin transition of iron in FeSiO 3 liquid at 2500–6000 K and pressure conditions spanning the entire mantle using first‐principles molecular dynamics simulations. Our calculations predict that FeSiO 3 liquid undergoes a linear high‐to‐low spin transition over a broad pressure interval (>296 GPa), and the spin state of iron in FeSiO 3 liquid is mainly the high‐spin state near the conditions of the core‐mantle boundary. Our results of FeSiO 3 liquid adiabats show that iron content has little effect on the adiabatic temperature profile of liquid (Mg,Fe)SiO 3 in a magma ocean.