6533b82cfe1ef96bd128eb7c

RESEARCH PRODUCT

Importance of Triples Contributions to NMR Spin–Spin Coupling Constants Computed at the CC3 and CCSDT Levels

Rasmus FaberJürgen GaussStephan P. A. Sauer

subject

Coupling constant010304 chemical physicsBasis (linear algebra)ChemistryNuclear magnetic resonance spectroscopy010402 general chemistry01 natural sciences0104 chemical sciencesComputer Science ApplicationsCoupled cluster0103 physical sciencesPhysical and Theoretical ChemistryAtomic physicsSpin-½Second derivative

description

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 ...

yearjournalcountryeditionlanguage
2016-12-20Journal of Chemical Theory and Computation
https://doi.org/10.1021/acs.jctc.6b01003