Simulation of bulk Earth compositional melt system: Insight into metal-silicate differentiation during the planetary accretion

To gain insight into the chemical evolution of Earth during the accretion, we have been simulating a mixed metallic liquid-silicate magma ocean system using deep potential molecular dynamics (DPMD). Our supercell configurations correspond to a bulk Earth composition consisting of four major elements, namely Fe, Mg, Si, and O in the amounts of 35.5,18.9, 15.4, and 30.2 wt.%, respectively. Deep potentials were first obtained by training first-principles energy and force results for 520-atom supercell (Fe86Mg105Si74O255). Then long DPMD simulations were performed for Fe1376Mg1680Si1184O4080 melt system (total 8320 atoms) at different conditions of pressure and temperature. Visualization of the simulated atomic position-time series indicates a chemical phase separation of the system into iron-rich region and iron-poor region which apparently correspond to metallic core and silicate magma ocean, respectively. Based on our preliminary analysis of local bonding and coordination environments, the iron-rich region also incorporates Si and O in significant amounts of about 15 and 5 atom %, respectively, but almost no Mg. On the other hand, the iron-poor region (~10 atom % Fe) is comprised of Mg, Si and O which appears to resemble a pyrolytic composition. To accurately characterize such predicted chemical phase separation and infer the composition of each phase requires a detailed spatial (geometrical) and temporal analysis of simulation outputs which is currently in progress.