paper

Phase transformation in boron under shock compression

arXiv:2001.11890 · doi:10.1016/j.solidstatesciences.2020.106376

Abstract

Using first-principles molecular dynamics, we calculated the equation of state and shock Hugoniot of various boron phases. We find a large mismatch between Hugoniots based on existing knowledge of the equilibrium phase diagram and those measured by shock experiments, which could be reconciled if the $I^\pm$ -B $_{12}$ / $I^^{2} \to I^^{3}$ -B $_{28}$ transition is significantly over-pressurized in boron under shock compression. Our results also indicate that there exists an anomaly and negative Clapeyron slope along the melting curve of boron at 100 GPa and 1500--3000 Kelvin. These results enable in-depth understanding of matter under shock compression, in particular the significance of compression-rate dependence of phase transitions and kinetic effects in experimental measurements.

18 pages, 5 figures (1 in graphical abstract)