Revisiting the effect of shear stress on the γ→α phase transition of cerium under shock loading

Abstract

The dynamic response of Cerium under high pressure and temperature is not clear due to the complexity of its phase diagram. Using large-scale atomistic simulations, we report the γ→α phase transition (PT) of Ce under shock loading. The PT behaviors predicted by present simulations are in reasonable agreement with previous experiments, thus confirm the validity of the interatomic potential. While the simulated wave velocities of elastic precursor are larger than experiments, the PT wave velocities agree well with the LASL data. In the T-P phase diagram, the Hugoniot states generally agree with the lower-pressure extrapolation of the higher-pressure experimental data, but differ significantly from each other orientations. By examining the ratio between the shear stress and hydrostatic stress, it is found that the anisotropic response of PT kinetics might be dependent on the variance of shear stress with lattice orientations. The present study suggests that the effect of shear stress usually ignored in shock wave experiments has to be treated seriously when studying the low-pressure γ→α PT of Ce.