Summary: Electron correlation from path resummations: the double-excitation star
Alex J. W. Thom,
George H. Booth, and Ali Alavi
University of Cambridge, Chemistry Department, Lensfield Road, Cambridge CB2 1EW, U. K.
(Dated: November 12, 2007)
Resummation over a selected subset of paths allows the approximate evaluation of a N-electron
path-integral. In particular, we show that the double excitation star graph, consisting of all doubly
excited determinants attached to the reference HartreeFock determinant, has an energy which is
easily calculated in O
time after integral precomputation, and produces binding curves of a
similar quality to CCSD theory for a range of systems including the N2 molecule, the hydrogen-
bonded water dimer, and dispersion dominated Ne2 and Ar2 dimers.
The calculation of the electronic correlation energy of
a molecule is fundamental for an accurate description
of inter- and intra-molecular interactions. The usual
wavefunction-based approaches are based on many-body