Multiphase extension of plasticity model for high energy density conditions

We recently demonstrated that continuum-level plasticity can be described well for polycrystalline materials in the high energy density (HED) regime, using a single dislocation density and single mobility mechanism calibrated from electronic structure theory, with a single empirical parameter related to the Peierls barrier. We used the atom-in-jellium model for efficiency and wide-ranging predictions, but this model is restricted to elements, is relatively inaccurate at low pressures, and cannot account for polymorphism. Here we extend the calibration of the plasticity model to multiple phases, using multi-ion electronic structure calculations that are more accurate at low pressure and are not limited to elements. A separate calibration of the Peierls barrier parameter is needed for each phase. We demonstrate the calibration and predicted strength behavior for several materials of current interest in HED studies.