Improving upon CCSD(TQ(f)) for potential energy surfaces: ΛCCSD(TQ(f)) models.
We consider classes of noniterative (∼n(7)) ΛCCSD(TQ(f)) (coupled cluster singles and doubles with noniterative triples and quadruples) for bond breaking including approximations based on Λ(2)CCSD(TQ(f)). All methods are applied to the standard tests for the treatment of potential energy curves for small molecules (HF, F(2), H(2)O, N(2), and C(2)) where unambiguous comparison to full configuration interaction exists. Depending on the nature of the electron correlation substantial improvements are obtained at the same ∼n(7) cost over CCSD(T).
Musial
Monika
M
Institute of Chemistry, University of Silesia, Szkolna 9, Katowice 40-006, Poland. musial@qtp.ufl.edu
Bartlett
Rodney J
RJ