PAIR DENSITY-FUNCTIONAL THEORY - A GENERALIZED DENSITY-FUNCTIONAL THEORY

The idea of a pair density functional theory for fermions is presented . Whereas in the conventional Hohenberg-Kohn-Sham theory for the groun d state of an interacting N-particle system the particle density is th e key quantity and the sum of the kinetic and the interaction energy i s a universal functional of this density, here the pair distribution f unction (PDF) is the key quantity and the kinetic energy alone is a un iversal functional of this PDF. With an appropriate ansatz for the PDF and the kinetic energy in terms of antisymmetric geminals a two-parti cle equation with an effective local interaction potential and a corre sponding expression for the total energy are derived. Besides this a w ay is described how to obtain from the solution of the effective two-p article equation also the one-particle density matrix via the first li nk of the equation of motions for the reduced density matrices.