Scalar relativistic correction to nucleus-independent chemical shifts of coinage-metal compounds: How does the pseudopotential approximation perform?

The performance of commonly used pseudopotentials for calculations of nucleus-independent chemical shifts (NICS) at the center of coinage-metal rings (M4Li2 (D4h), M = Cu, Ag, Au) is investigated. The scalar relativity, which has a non-negligible effect on NICS, is found to be accurately described by the pseudopotential approximation. Overall, good agreement is obtained with all-electron relativistic methods, however, careful comparisons with these calculations and consideration for large triple-ζ basis sets are recommended when aiming to accurately define the relative degree of diatropicity among a series of compounds.