Calculation of phase-dependent optical absorption in materials

We calculate the optical absorption spectra of different phases of various materials (Al, Bi, Fe) in an effort to support work in which optical constants are measured during the course of a shock compression experiment. In addition to showing that the optical properties of various solid phases of a given material are quite different, we compute the optical properties of Al across its solid-to-liquid transition and show that a prominent peak in the spectrum of the solid smoothly disappears as the temperature is raised above Tmelt. This is in agreement with earlier measurements on solid and liquid Al, but is in disagreement with a more recent measurement on the liquid. Our results suggest that in situ optical constants measurements may be used as a diagnostic for the shock melting of Al.