Premium
Inclusion of the (T) triples correction into the linear‐ r 12 corrected coupled‐cluster model CCSD(R12)
Author(s) -
Fliegl Heike,
Hättig Christof,
Klopper Wim
Publication year - 2006
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.20991
Subject(s) - coupled cluster , extrapolation , basis set , ansatz , basis (linear algebra) , orthonormal basis , chemistry , physics , mathematical physics , quantum mechanics , mathematics , molecule , mathematical analysis , geometry
The recently developed singles‐and‐doubles linear‐ r 12 corrected coupled‐cluster model CCSD(R12) has been extended by inclusion of triples corrections in exactly the same manner as in the popular CCSD(T) model. The resulting model is denoted CCSD(T)(R12). An orthonormal auxiliary basis set is used for the resolution‐of‐the‐identity approximation to calculate the three‐ and four‐electron integrals needed in the linear‐ r 12 Ansatz. CCSD(T)(R12) reaction energies are calculated for a test set of 15 chemical reactions involving 23 small molecules. The CCSD(T)(R12), CCSD(R12), and MP2‐R12 results are compared with experimental data obtained by correcting experimental enthalpies of reaction for zero‐point vibrational energies and finite temperature contributions. Conventional MP2, CCSD, and CCSD(T) results are presented for comparison. An estimate of the basis set limit is obtained by an aug‐cc‐pV(Q + d)Z/aug‐cc‐pV(5 + d)Z CCSD(T) extrapolation for a subset of 12 reactions. All CCSD(T) results are compared with the extrapolated values, and the errors are analyzed for the CCSD(T) and CCSD(T)(R12) models in various basis sets. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006