APPROXIMATE ONE-ELECTRON DENSITY-MATRIX FUNCTIONALS FOR THE ELECTRON-ELECTRON REPULSION ENERGY FROM THE HYPERVIRIAL THEOREM

Application of the hypervirial theorem to a certain class of two-elect ron operators yields the electron-electron repulsion energy as an appr oximate functional of the Hartree-Fock one-electron reduced density ma trix. This functional is entirely parameterized by a single screening function that, upon the assumption of transferability, can be readily retrieved from the known correlation energy of the homogeneous electro n gas. Invoking the properties of the actual electronic Hamiltonian, t he new formalism explicitly incorporates dispersion effects that are n ot accounted for by the conventional density functional approaches. Ev en more importantly, it affords analogous functionals for other variat ional methods such as Monte Carlo self-consistent field (MC SCF). Sinc e such functionals are bi- and trilinear in the occupied orbitals, the ir fully analytical computation should be feasible with a carefully ch osen approximate representation of the screening function. (C) 1998 Am erican Institute of Physics.