We describe the challenges involved when using time-dependent density
functional theory (TDDFT) to describe warm dense matter (WDM) within a
plane-wave, real-time formulation. WDM occurs under conditions of
temperature and pressure (over 1000 K and 1 Mbar) where plasma physics
meets condensed matter physics. TDDFT is especially important in this
regime as it can describe ions and electrons strongly out of equilibrium.
Several theoretical challenges must be overcome including assignment of
initial state orbitals, choice of time-propogation scheme, treatment of PAW
potentials, and inclusion of non-adiabatic effects in the potential energy
surfaces. The results of these simulations are critical in several
applications. For example, we will explain how the TDDFT calculation can
resolve modeling inconsistencies in X-ray Thompson cross-sections, thereby
improving an important temperature diagnostic in experiments. Sandia
National Laboratories is a multi-program laboratory managed and operated by
Sandia Corporation, a wholly owned subsidiary of Lockheed Martin
Corporation, for the U.S. Department of Energy's National Nuclear Security
Administration under contract DE-AC04-94AL85000.