Is reduced-density-matrix functional theory a suitable vehicle to import   explicit correlations into density-functional calculations?
  A variational formulation for the calculation of interacting fermion systems based on the density-matrix functional theory is presented. Our formalism provides for a natural integration of explicit many-particle effects into standard density-functional-theory based calculations and it avoids ambiguities of double-counting terms inherent to other approaches. Like the dynamical mean-field theory, we employ a local approximation for explicit correlations. Aiming at the ground state only, trade some of the complexity of Green's function based many-particle methods against efficiency. Using short Hubbard chains as test systems we demonstrate that the method captures ground state properties, such as left-right-correlation, beyond those accessible by mean-field theories. 
Peter E. Bloechl, Christian F. J. Walther, Thomas Pruschke
cond-mat.str-el