Abstract

This seminar presents a systematic study of partitioning schemes for locally dense basis sets in the context of NMR shielding calculations. The partitionings explored were based exclusively on connectivity and utilized the basis sets from the pcS-n series. Deviations from pcS-4 shieldings were calculated for a set of 28 organic molecules at the HF, B3LYP and KT3 levels of theory, with the primary goal being the determination of an efficient scheme that achieves maximal deviations of 0.1ppm for ¹H and 1ppm for ¹³C. Both atom based and group based divisions of basis sets were examined, with the latter providing the most promising results. It is demonstrated that for the systems studied, at least pcS-1 is required for all parts of the molecule. This, coupled with pcS-3 on the group of interest and pcS-2 on the adjacent groups, is sufficient to achieve the desired level of accuracy at a minimal compuational expense.