MD simulation of steady shock-wave fronts with phase transition in single-crystal iron

Abstract

Overdriven shock waves propagating in main crystallographic directions of single-crystal bcc iron were studied with moving-window molecular dynamics (MD) technique. To simulate correctly the shock-induced bcc-to-hcp phase transition in iron a new EAM potential fitted to the cold pressure curves and pressure transition at 13 GPa was developed with the stress matching method. We demonstrate that structure of shock fronts depends on orientation of crystal. A peculiar structure of steady shock-wave front in [100] direction is observed. While the ultra-fast α → e transition initiated in uniaxially compressed crystal along [100] in elastic zone transforms bcc completely to hcp phase, transformation in other directions is performed only partially with production of metastable composition of nanometer-sized bcc-hcp-fcc grains.