DENSITY FUNCTIONAL AND NON.EQUILIBRIUM METHODS FOR UNUSUAL STATES OF MATTER PRODUCED USING SHORT-PULSE LASERS Chandre Dhanna-wardana Institute for Microstructural Sciences National Research Council of Canada Ottawa, Canada KIAOR6 INTRODUCTION Density functional theory (DFf)1-3 has proved itself as a very effective first principles calculational method for describing the electronic and structural properties of atoms, solids, liquids and plasmas. DFT is, of course, a method for equilibrium ensembles. However, using the output of DFT calculations as the input to non-equilibrium field-theory techniques, we obtain an extremely versatile theoretical framework which is not just a formal method, but an effective calculational method for confronting experimental results via first principles calculations. Just such a versatile and powerful tool is needed to understand the new states of matter that are being produced by the use of short-pulse lasers to compress, heat, ionize and manipulate matter into very unusual non-equilibrium situations. Such non-equilibrium situations are experimentally monitored using time- resolved probes which provide information on time dependent populations, optical and carrier transport coefficients, linear and non-linear susceptibilities, etc. It is clear from the talks by Profs. Mike Downer, Tom Hall, and von der Linde, that the time evolution of such systems during energy deposition by the laser may involve the transformation of the solid to other solid phases, to a liquid and finally to a plasma. Hence the first principles method must have the capability of spanning such a variety of regimes of condensed matter. In this short review article we begin by a simple discussion of DFT, illustrating it with pertinent calculations. Then we consider transport coefficients from the point of view of non-equilibrium statistical mechanics, where we briefly state results which can be rigorously obtained using methods of non-equilibrium green functions'[ (e.g., the Keldysh method, Zubarev's methods, methods based on thermal-field dynamics). The stated results will be made plausible by simple Fermi golden rule type arguments which lead to generalizations of Kogan's formula for the energy transfer between different subsystems. These formulae need densities of states, scattering amplitudes and basic structure parameters (e.g., the ionic structure factor) which are provided by DFT. As illustrations of these approaches we will discuss calculations for "liquid" carbon, silicon and germanium, the shift of the K-edge of compressed-Al along the shock Hugoniot, and energy transfer from hot electrons to colder ions, as happens in many short- pulse laser experiments. The slowness in the energy transfer between electrons and ions has been exploited in recent short-pulse experiments to generate "solids" containing electrons at extremely high temperatures. Thus the static and dynamic conductivity cr(ro) of "solid" aluminum containing electrons close to 1()6 Kelvin will be examined. Laser Interactions with: Atoms . Solids. and Plasmas Edited by R.M. More. Plenum Press. New York. 1994 311