Analytic second derivatives for the full coupled-cluster singles, doubles, and triples model: Nuclear magnetic shielding constants for BH, HF, CO, N2, N2O, and O3

An implementation of analytic second derivatives for the coupled-cluster singles, doubles, and triples (CCSDT) model is reported and applied to the calculation of nuclear magnetic shielding constants of BH, HF, CO, N2, N2O, and O3. The CCSDT calculations yield further evidence for the high accuracy provided by chemical shift calculations employing the coupled-cluster singles, doubles (CCSD) approach augmented by a perturbative triples correction CCSD(T).