Large-Scale Classical Molecular Dynamics Simulations of Shock-Induced Plasticity in bcc Niobium

Large-scale classical molecular dynamics simulations are used to study the response of bcc Nb to shock compression, for perfect crystals in the [100] and [110] orientations. An embedded atom method (EAM) potential due to Johnson and Oh is used to describe the interatomic forces. Both orientations appear to plastically deform primarily by twinning, and we observe a bcc-hcp phase transformation at shock pressures above $\sim $75 GPa. There is no experimental evidence for any such transformation in Nb, although a similar transformation occurs in Fe and other bcc metals, so it is likely that this is an artifact of the EAM potential.