Embedded atom model for liquid metals: Liquid iron

Abstract

A method for calculating the embedded atom model potential suggested earlier for liquid Ga and Bi uses data on the structure and thermodynamic properties of metals close to their melting points. This method was applied to liquid iron at temperatures and pressures up to 5000 K and 360 GPa. Several iron models with the potential of the embedded atom model were constructed by the method of molecular dynamics at temperatures from 1820 to 5000 K and densities from 8.00 to 12.50 g/cm3. The thermodynamic, structural, diffusion, and viscosity properties of iron were calculated. The self-diffusion coefficients decreased almost linearly as the volume of the system became smaller. The conclusion is drawn that iron in the external region of the Earth’s core behaves as a liquid with self-diffusion coefficients of about ∼10-5 cm2/s and viscosity ∼10-3−10-2 Pa s. At the boundary between the external and inner core regions, at densities of 11–12 g/cm3, iron has the properties of an amorphous phase and its self-diffusion coefficient becomes too low to be estimated by the method of molecular dynamics. Under the Earth’s inner core conditions, the embedded atom model of iron spontaneously crystallizes.