Density functional theory from the extreme limits of correlation

摘要

Densify functional perturbation theory for the correlation energy E_c[rho] is equivalent to the Taylor expansion of the coupling-constant integrand W_(alpha)[rho] around its weak-interaction limit alpha -> 0. While this theory appears to diverge for many systems of interest (atoms,molecules, etc). the opposite limit alpha -> infinity of strong interaction (which is mathematically simple) appears to provide just the missing information. Only the two leading terms to the perturbation expansion in the weakinteraction limit are required for an accurate prediction of E_c[rho] if they are extrapolated properly to the strong-interaction limit. This interaction-strength interpolation is demonstrated here for the helium atom, where the strong - interaction limit can be treated rigorously. For general systems with more than two electrons, simple explicit approximations to that limit are available.