Incorporating a completely renormalized coupled cluster approach into a composite method for thermodynamic properties and reaction paths

TitleIncorporating a completely renormalized coupled cluster approach into a composite method for thermodynamic properties and reaction paths
Publication TypeJournal Article
Year of Publication2012
AuthorsNedd SA, DeYonker NJ, Wilson AK, Piecuch P, Gordon MS
Journal TitleJournal of Chemical Physics
Date Published04
Type of ArticleArticle
ISBN Number0021-9606
Accession NumberWOS:000303146800011
Keywordsatoms al-ar, BASIS-SETS, bond additivity corrections, coefficient correlation method, configuration-interaction, consistent, correlated molecular calculations, gaussian-basis, open-shell systems, quadratic, quantum-chemistry, set model chemistry, sets

The correlation consistent composite approach (ccCA), using the S4 complete basis set two-point extrapolation scheme (ccCA-S4), has been modified to incorporate the left-eigenstate completely renormalized coupled cluster method, including singles, doubles, and non-iterative triples (CR-CC(2,3)) as the highest level component. The new ccCA-CC(2,3) method predicts thermodynamic properties with an accuracy that is similar to that of the original ccCA-S4 method. At the same time, the inclusion of the single-reference CR-CC(2,3) approach provides a ccCA scheme that can correctly treat reaction pathways that contain certain classes of multi-reference species such as diradicals, which would normally need to be treated by more computationally demanding multi-reference methods. The new ccCA-CC(2,3) method produces a mean absolute deviation of 1.7 kcal/mol for predicted heats of formation at 298 K, based on calibration with the G2/97 set of 148 molecules, which is comparable to that of 1.0 kcal/mol obtained using the ccCA-S4 method, while significantly improving the performance of the ccCA-S4 approach in calculations involving more demanding radical and diradical species. Both the ccCA-CC(2,3) and ccCA-S4 composite methods are used to characterize the conrotatory and disrotatory isomerization pathways of bicyclo[1.1.0]butane to trans-1,3-butadiene, for which conventional coupled cluster methods, such as the CCSD(T) approach used in the ccCA-S4 model and, in consequence, the ccCA-S4 method itself might fail by incorrectly placing the disrotatory pathway below the conrotatory one. The ccCA-CC(2,3) scheme provides correct pathway ordering while providing an accurate description of the activation and reaction energies characterizing the lowest-energy conrotatory pathway. The ccCA-CC(2,3) method is thus a viable method for the analyses of reaction mechanisms that have significant multi-reference character, and presents a generally less computationally intensive alternative to true multi-reference methods, with computer costs and ease of use that are similar to those that characterize the more established, CCSD(T)-based, ccCA-S4 methodology. (C) 2012 American Institute of Physics. []

URL<Go to ISI>://WOS:000303146800011
Alternate JournalJ. Chem. Phys.