Coupled-Perturbed Scheme for the Calculation of Electronic g-Tensors with Local Hybrid Functionals

A coupled-perturbed Kohn-Sham (CPKS) scheme for calculating second-order magnetic properties has been developed for the case of general occupied-orbital-dependent (OOD) exchange-correlation functionals involving the exact-exchange energy density. The origin of the coupling terms in the functional derivatives of OOD functionals with respect to the orbitals has been thoroughly analyzed, and general expressions for the resulting coupling terms have been obtained. The generalized CPKS scheme thus obtained has been implemented within the MAG-ReSpect code and tested in calculations of electronic g-tensors with local hybrid functionals. Compared to previously tested global hybrids, like B3LYP, thermochemically optimized local hybrids provide only little to moderate improvement for test sets of main-group radicals and paramagnetic transition-metal complexes. Closer analyses point to possible areas in which the fundamentally more flexible local hybrids may be improved for the property at hand.