In principle, Time-Dependent Density Functional Theory (TDDFT) provides a very powerful tool for simulating the dynamics of matter. A real-time implementation of TDDFT should be able to capture the behavior and interactions of electron and hole excitations, excitons, and plasmons within a single computational paradigm, and when coupled to a system of ions evolving on molecular dynamics-like trajectories, the phonon degrees of freedom are also represented. In practice, there are several challenges associated with achieving the full promise of TDDFT including the choice of exchange-correlation functional, the interpretation of correlation functions, and the approach used to couple the ions and electrons. We discuss these challenges with emphasis on the specific problem of calculating the rate of energy exchange between electrons and ions at two different temperatures.
This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. Department of Energy, Office of Basic Energy Sciences user facility. 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.
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