Study of high temperature Be from first principles

We use first-principles simulations to study the optical properties and electron-electron relaxation times of beryllium (Be) at high temperatures to allow for the design of warm dense matter (WDM) optical conductivity experiments. Within the local-density approximation (LDA), we calculate the imaginary part of the macroscopic dielectric function, with intraband transitions accounted for by the Drude model, to find how the optical absorption of Be changes as a function of temperature from 0.5 to 3.0 eV. We find that absorption does not have a strong temperature dependence at low photon energies due to intraband transitions. For photon energies above 0.75 eV, we see that as temperature increases, the strength of absorption decreases, however the absorption occurs over a larger energy range. We also study electron-electron relaxation time through a GW approach, in which we fit the imaginary part of the self-energy to the Landau theory of the Fermi liquid to determine the lifetimes of electrons at energies above the Fermi energy. This work will lead to a better fundamental understanding of the optical and electronic properties of Be at high temperature and subsequent cooling, allowing for better design and interpretation of results of WDM experiments.