TitleA Companion Perturbation Theory for State-Specific Multireference Coupled Cluster Methods
Publication TypeJournal Article
Year of Publication2009
AuthorsEvangelista, FA, Simmonett, AC, Schaefer III, HF, Mukherjee, D, Allen, WD
JournalPhysical Chemistry Chemical Physics
ISBN Number1463-9076
Accession NumberISI:000266615600006
Keywordsconfiguration-interaction method, correlated molecular calculations, field reference function, gaussian-basis sets, model-space coefficients, open-shell systems, polarization basis functions, potential-energy surfaces, size-extensivity correction, spin-flip approach

A partitioning scheme is applied to the state-specific Mukherjee multireference coupled cluster method to derive a companion perturbation theory (Mk-MRPT2). A production-level implementation of Mk-MRPT2 is reported. The effectiveness of the Mk-MRPT2 method is demonstrated by application to the classic F-2 dissociation problem and the lowest-lying electronic states of meta-benzyne, including computations with up to 766 atomic orbitals. We show that Mk-MRPT2 theory is particularly useful in multireference focal point extrapolations to determine ab initio limits.

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