Uniform Electron Gas from Two-particle Wavefunctions

A common approach to the many-electron problem (atoms, molecules and solids) is its transformation into a fewer-particle problem. In Density Functional Theory 2 (DFT) one rewrites the ground-state energy of a many-electron system as a functional of just the one-electron density n(r), the diagonal part of the oneparticle reduced density matrix. In recent years, much attention has been devoted to approaches which rewrite the system energy as a functional of the oneor the two-particle reduced density matrix. With respect to DFT, these approaches have the advantage that the kinetic energy functional is known and that they provide more information about the many-body wavefunction. In this contest, the relevance of two-electron wavefunctions (geminals) has been pointed out: the use of an antisymmetrized geminal power wavefunction, i.e., a many-body wavefunction built in terms of geminals with the correct symmetry under particle permutation, provides the basis for a formally correct one-particle reduced density matrix functional theory.