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Paper
Phys. Chem. Chem. Phys., 2009, 11, 9677 - 9686, DOI: 10.1039/b910905f
Coulomb-only second-order perturbation theory in long-range-corrected hybrid density functionals
Benjamin G. Janesko and Gustavo E. Scuseria
We have been investigating the combination of a short-range density functional approximation with long-range random phase approximation (RPA) correlation, where the direct RPA correlation is constructed using only Coulomb (i.e., not antisymmetrized) two-electron integrals. Our group
s recently demonstrated connection between RPA and coupled cluster theory suggests investigating a related method: second-order Møller–Plesset perturbation theory correlation (MP2) constructed using only Coulomb integrals. This new 
JMP2
method is related to the scaled-opposite-spin SOS-MP2 approximation [Y. Jung, R. C. Lochan, A. D. Dutoi and M. Head-Gordon, J. Chem. Phys., 2004, 121, 9793], which is also constructed using only Coulomb integrals. While JMP2 and SOS-MP2 yield identical results for closed shell systems, they have important differences for open shells. We show here that both JMP2 and SOS-MP2 provide a reasonable treatment of long-range correlation when combined with a short-range exchange–correlation functional. Remarkably, JMP2s explicit inclusion of (approximate) like-spin correlation effects provides significant improvements over SOS-MP2 for thermochemistry.
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