Hugoniot States and Mie-Gruneisen Equation of State of Iron Estimated Using Molecular Dynamics

The objective of this study was to develop a micromechanical approach for determining the Mie-Gruneisen EOS parameters of iron under the Hugoniot states. The multiscale shock technique (MSST) coupled with molecular dynamics (MD) simulations was employed to describe the shocked Hugoniot relation of single-crystal (SC) and nanocrystalline (NC) iron under high pressures. The Mie-Gruneisen equation of state (EOS) parameters, the cold pressure (P-c), the cold energy (E-c), the Gruneisen coefficient (gamma), and the melting temperature (T-m) are discussed. The error between SC and NC iron results was found to be less than 1.5%. Interestingly, the differences in Hugoniot state (P-H) and the internal energy between SC and NC iron were insignificant, which shows that the effect of grain size (GS) under high pressures was not significant. The P-c and E-c of SC and NC iron calculated based on the Morse potential were almost the same with those calculated based on the Born-Mayer potential; however, those calculated based on the Born-Mayer potential were a little larger at high pressures. In addition, several empirical and theoretical models were compared for the calculation of gamma and T-m. The Mie-Gruneisen EOSs were shown on the 3D contour space; the pressure obtained with the Hugoniot curves as the reference was larger than that obtained with the cold curves as the reference.

Automated summary

This study developed a micromechanical approach to determine the Mie-Gruneisen EOS parameters of iron under Hugoniot states. The differences between single-crystal and nanocrystalline iron under high pressures were found to be insignificant, with slight variations in results calculated using different potentials.