Vibrational corrections to indirect nuclear spin-spin coupling constants calculated by density-functional theory

摘要

At the present level of electronic-structure theory, the differences between calculated and experimental indirect nuclear spin-spin coupling constants are typically as large as the vibrational contributions to these constants. For a meaningfl comparison with experient, it is therefore necessary to include vibrational corrections in the calcualted spin-spin coupling constants. In the present paper, such corrections have been calcualted for a number of small molecular systems by using hybrid density-functional theory (DFT), yielding results in good agreement with previous wave-function calculations. A set of empirical equilibrium spin-spin coupling constants has been compiled from the experimentally observed constants and the calculated vibrational corrections. A comparison of these empirical constants with calculations suggests the the restricted-active-space self-consistent field method is the best approach for calculating the indirect spin-spin coupling constants of small molecules, and that the second-order polarization propagator approach and DFT are similar in performance. To illustrate the usefulness of the presented method. the vibrational corrections to the indirect spin-spin coupling constants of the benzene molecule have been calculated.