Structure and dynamics of Fe90Si3O7 liquids close to Earth's liquid core conditions

Using an artificial neural-network machine learning interatomic potential, we have performed molecular dynamics simulations to study the structure and dynamics of ${\mathrm{Fe}}_{90}{\mathrm{Si}}_{3}{\mathrm{O}}_{7}$ liquid close to the Earth's liquid core conditions. The simulation results reveal that the short-range structural order (SRO) in the ${\mathrm{Fe}}_{90}{\mathrm{Si}}_{3}{\mathrm{O}}_{7}$ liquid is very strong. About 80% of the atoms are arranged in crystallinelike SRO motifs. In particular, $\ensuremath{\sim}70%$ of Fe-centered clusters can be classified as either hexagonal-close-packed-like or icosahedrallike SRO motifs. The SRO clusters centered on Fe, Si, or O atoms are strongly intermixed and homogenously distributed throughout the liquid. The atomic structure of the liquid and the fractions of dominant SRO clusters are not sensitive to pressure/temperature used in the simulations except that the SRO of the O-centered clusters is enhanced close to inner core pressures. The O-diffusion coefficient is about two to three times larger than the Fe and Si ions and increases more rapidly in the deeper core regions.