TITLE

The weak orthogonality functional in explicitly correlated pair theories

AUTHOR(S)
Tew, David P.; Klopper, Wim; Manby, Frederick R.
PUB. DATE
November 2007
SOURCE
Journal of Chemical Physics;11/7/2007, Vol. 127 Issue 17, p174105
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Recent advances have seen the convergence of the R12 and Gaussian geminal explicitly correlated methods, such that the principal remaining distinction is the way in which the many-electron integrals are handled. Here we examine the weak orthogonality functional and the resolution of the identity and find that the first, although exact in the limit of infinite basis, introduces a conflict between the physical description of the electronic cusp and the satisfaction of the strong orthogonality constraint. This leads us to propose an improved weak orthogonality functional where the explicitly correlated pair functions are almost orthogonal to the occupied orbitals by construction. For applications where 95%-98% accuracy in the total correlation energy is sufficient, we recommend use of the strong orthogonality functional in combination with the resolution of the identity for three- and four-electron integral evaluations.
ACCESSION #
27457969

 

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