Yutong Yang

We show with molecular dynamics simulations that spinodal decomposition is a probable initiation mechanism of spallation in impact-melted samples at extremely high strain rates. The formation of voids or bubbles is a secondary process following the spinodal amplification of density fluctuations. As a result, the spallation strength can be related to the inherent thermodynamic property of the liquid, i.e., the liquid-gas spinodal curve, which can be determined by independent equation-of-state studies in prior. This connection between high strain-rate spallation and spinodal decomposition may be further examined in future experiments.

The thermodynamic properties of boron nitride under extreme pressures and temperatures are of great interest and importance for materials science and inertial confinement fusion physics, but they are poorly understood owing to the challenges of performing experiments and realizing ab initio calculations. Here, we report the first shock Hugoniot data on hexagonal boron nitride at pressures of 5–16 Mbar, using hohlraum-driven shock waves at the SGIII-p laser facility in China. Our density functional theory molecular dynamics calculations closely match experimental data, validating the equations of state for modeling the shock response of boron nitride and filling a crucial gap in the knowledge of boron nitride properties in the region of multi-Mbar pressures and eV temperatures. The results presented here provide fundamental insights into boron nitride under the extreme conditions relevant to inertial confinement fusion, hydrogen–boron fusion, and high-energy-density physics.