Local correlation potentials from Brueckner coupled-cluster theory.
Local correlation potentials have been obtained from the nonlocal Brueckner coupled-cluster correlation potentials for the rare-gas atoms He, Ne, and Ar and the CO molecule. It is shown that the local correlation potential can mainly be expressed as a sum of two components: a "pure" correlation part and a relaxation contribution. While the total correlation potentials show an oscillating behavior near the nuclei, indicating the atomic shell structure, their components decrease rather monotonously, with a step structure in case of Ne and Ar. By looking at the determinantal overlap and one-electron properties it has been found that the orbitals obtained from these local potentials form a determinant which very well corresponds with the Brueckner determinant. Thus the previously found closeness between the Hartree-Fock determinant and the exchange-only Kohn-Sham determinant [Della Sala and Gorling, J. Chem. Phys. 115, 5718 (2001)] is confirmed also for the correlated case.
Hesselmann
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Center of Theoretical Chemistry, Arhus University, Denmark. and@chem.au.dk