Molecular dynamics simulation of shock compression of metals: Iron and iron-sulfur solutions

Abstract

The embedded atom model potential suggested earlier was improved to correctly describe iron at high pressures and temperatures. Correction was introduced using the shock compression data. The properties of body- and face-centered cubic (BCC and FCC) lattices and liquid iron at compression degrees up to 50% of the normal volume and temperatures up to 10000 K were calculated. At degrees of compression 0.7–0.6 and 0 K, the FCC lattice is thermodynamically stable. The temperature of fusion increases to ≈9700 K at compression to 50% of initial volume (pressure 585 GPa). The pressure of pure iron at 5000 K and density 12.5 g/cm3 is ≈250 GPa and is substantially lower than in the center of the Earth according to the geophysical data (360 GPa). An embedded atom model potential for a 10 at % solution of sulfur in iron which allows the properties of the melt in the center of the Earth to be described correctly is suggested; the viscosity of the melt under these conditions is not high (0.0156 Pa s); these results are close to those obtained in ab initio calculations. The possibility of partial Earth core crystallization is shown.