Modeling Laser-Driven High-Rate Plasticity in BCC Lead

We discuss the constitutive modeling of lead in the high-pressure body-centered cubic (bcc) phase. Constitutive models for lead in the literature are calibrated to experiments in the low-pressure face-centered cubic (fcc) phase. The Steinberg-Guinan model for pure lead is one such model. As an assessment of the effect of different crystal structure at high pressure, we construct a model for the bcc phase. The model is in the Improved Steinberg-Guinan form, with the pressure hardening determined by first-principles calculations of the pressure dependence of the shear modulus. The constitutive models have been run in continuum simulations of high-pressure deformation experiments as a test of the models. High-energy laser platforms such as the National Ignition Facility (NIF) can probe plasticity at extremely high pressures and rates in largely shock-free ramp-compression waves. Here we consider experiments on lead at peak pressures of similar to 350-500 GPa and strain rates of similar to 10(7)/s.