Exchange representations in Kohn–Sham NMR shielding calculations

The treatment of orbital exchange in density functional theory (DFT) hybrid functionals is investigated in the context of NMR shielding constants. High-quality shieldings are obtained using the MKS approach with a ZMP exchange-correlation potential determined from the hybrid density. Comparable results are obtained using an appropriately-scaled ZMP exchange-only potential, together with the hybrid multiplicative component. Replacing the ZMP exchange potential in this scheme with the LHF potential of Della Sala and Gِrling is less successful, highlighting a difference between ZMP and LHF exchange. Unlike ZMP, the LHF exchange potential already provides reasonable quality uncoupled shieldings.