Scaling reduction of the perturbative triples correction (T) to coupled cluster
theory via Laplace transform formalism
P. Constans, P. Y. Ayala, and G. E. Scuseria. Scaling reduction of the
perturbative triples correction (T) to coupled cluster theory via Laplace transform
formalism. Journal of Chemical Physics, 113, 10451-10458 (2000).
A reformulation of the perturbative triples correction to coupled cluster singles
and doubles (CCSD) based on the numerical Laplace transform of the energy
denominator is presented. Rearranged equations reduce the
O(N7) canonical scaling to O(N6),
where N is a size measure of the electronic system. Two to three quadrature
points is adequate for chemical predictions. The Laplace ansatz permits simple,
noniterative expressions in noncanonical orbital representations. Furthermore,
substituting canonical by generalized CCSD natural orbitals, the Laplace ansatz
exhibits scaling close to O(N5), while retaining accuracy
and providing crossover with respect to canonical triples for small size systems. A
developing atomic orbital formulation is also introduced.
Molecular electronic-structure, density-functional theories, local correlation
treatment, atomic orbital basis, Gaussian-basis sets, full CCSDT model,
configuration-interaction, correlation energies, wave-functions, implementation.
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