A real-space model of nondynamical correlation

Local density-functional exchange-correlation approximations perform remarkably well in simulating nondynamical or "left-right" correlation in molecular bonds. Yet, they do so in a haphazard and unintentional way. In this work we carefully examine the nature of left-right correlation in multicenter systems and suggest a new nondynamical correlation model of post-Hartree-Fock style. The conventional approach to nondynamical correlation is based on the mixing of nearly degenerate states in electronic configuration space. Our approach, on the other hand, is based entirely in real space and uses a single determinant only. (C) 2003 American Institute of Physics.