Importance of triples contributions to NMR spin-spin coupling constants computed at the CC3 and CCSDT levels

TY - JOUR

T1 - Importance of triples contributions to NMR spin-spin coupling constants computed at the CC3 and CCSDT levels

AU - Faber, Rasmus

AU - Sauer, Stephan P. A.

AU - Gauss, Jürgen

PY - 2017/2/14

Y1 - 2017/2/14

N2 - We present the first analytical implementation of CC3 second derivatives using the spin-unrestricted approach. This allows, for the first time, the calculation of nuclear spin-spin coupling constants (SSCC) relevant to NMR spectroscopy at the CC3 level of theory in a fully analytical manner. CC3 results for the SSCCs of a number of small molecules and their fluorine substituted derivatives are compared with the corresponding coupled cluster singles and doubles (CCSD) results obtained using specialized basis sets. For one-bond couplings the change when going from CCSD to CC3 is typically 1-3%, but much higher corrections were found for 1JCN in FCN, 15.7%, and 1JOF in OF2, 6.4%. The changes vary significantly in the case of multibond couplings, with differences of up to 10%, and even 13.6% for 3JFH in fluoroacetylene. Calculations at the coupled cluster singles, doubles, and triples (CCSDT) level indicate that the most important contributions arising from connected triple excitations in the coupled cluster expansion are accounted for at the CC3 level. Thus, we believe that the CC3 method will become the standard approach for the calculation of reference values of nuclear spin-spin coupling constants.

AB - We present the first analytical implementation of CC3 second derivatives using the spin-unrestricted approach. This allows, for the first time, the calculation of nuclear spin-spin coupling constants (SSCC) relevant to NMR spectroscopy at the CC3 level of theory in a fully analytical manner. CC3 results for the SSCCs of a number of small molecules and their fluorine substituted derivatives are compared with the corresponding coupled cluster singles and doubles (CCSD) results obtained using specialized basis sets. For one-bond couplings the change when going from CCSD to CC3 is typically 1-3%, but much higher corrections were found for 1JCN in FCN, 15.7%, and 1JOF in OF2, 6.4%. The changes vary significantly in the case of multibond couplings, with differences of up to 10%, and even 13.6% for 3JFH in fluoroacetylene. Calculations at the coupled cluster singles, doubles, and triples (CCSDT) level indicate that the most important contributions arising from connected triple excitations in the coupled cluster expansion are accounted for at the CC3 level. Thus, we believe that the CC3 method will become the standard approach for the calculation of reference values of nuclear spin-spin coupling constants.

KW - Faculty of Science

KW - NMR Spectroscopy

KW - Spin-spin coupling constant

KW - Quantum Chemistry

KW - Computational Chemistry

KW - Coupled Cluster

KW - reference data

UR - http://pubs.acs.org/doi/suppl/10.1021/acs.jctc.6b01003/suppl_file/ct6b01003_si_001.pdf

U2 - 10.1021/acs.jctc.6b01003

DO - 10.1021/acs.jctc.6b01003

M3 - Journal article

C2 - 27992184

SN - 1549-9618

VL - 13

SP - 696

EP - 709

JO - Journal of Chemical Theory and Computation

JF - Journal of Chemical Theory and Computation

IS - 2

ER -