Optical properties of Al at shock-melt conditions

We report calculations of the linear optical absorption spectra of aluminum at pressures of roughly 1 Mbar and temperatures of around 5000 K. Both the hot fcc solid and the liquid have been studied at those conditions, and we conclude that it should be possible to distinguish solid from liquid when Al has been shocked. This suggests that in situ measurements of optical constants may serve as a diagnostic for melting in dynamic high pressure experiments. Calculations were performed using a combination of ab initio and semi-empirical electronic structure schemes, together with a combination of molecular dynamics schemes to generate snapshots of hot solid and liquid ionic configurations. Lower densities and temperatures were considered as well, showing favorable comparison with ambient pressure high-T optical measurements on Al.