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 for multi-bond 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 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 for multi-bond 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 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
VL - 13
SP - 696
EP - 709
JO - Journal of Chemical Theory and Computation
JF - Journal of Chemical Theory and Computation
SN - 1549-9618
IS - 2
ER -