Friday, August 24, 2012

1208.4703 (Tim Baldsiefen et al.)

Reduced density matrix functional theory at finite temperature. I.
Theoretical foundations

Tim Baldsiefen, E. K. U. Gross
An ab-initio approach to the description of grand canonical ensembles in thermal equilibrium, having local or nonlocal external potentials, will be presented. To this end a variational principle for the grand potential \Omega\ of the system under consideration with respect to its one-reduced density matrix \gamma\ will be established. The domain of \Omega[\gamma] will be shown to be determined by a simple set of constraints, making it suitable for numerical minimization. We will furthermore prove the existence of an analogon to the Kohn-Sham system of density functional theory, i.e. a system of noninteracting particles reproducing the one-reduced density matrix of the interacting system at finite temperature. Starting from this Kohn-Sham system as unperturbed system, we deduce a many-body approach to iteratively construct approximate functionals for the grand potential.
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