Density functional calculations of electronic g-tensors using spin-orbit pseudopotentials and mean-field all-electron spin-orbit operators

Modern density-functional methods for the calculation of electronic g-tenso rs have been implemented within the framework of the deMon code. All releva nt perturbation operators are included. Particular emphasis has been placed on accurate yet efficient treatment of the two-electron spin-orbit terms. At an all-electron level, the computationally inexpensive atomic mean-field approximation is shown to provide spin-orbit contributions in excellent ag reement with the results obtained using explicit one- and two-electron spin -orbit integrals. Spin-other-orbit contributions account for up to 25-30% o f the two-electron terms and may thus be non-negligible. For systems contai ning heavy atoms we use a pseudopotential treatment, where quasirelativisti c pseudopotentials are included in the Kohn-Sham calculation whereas approp riate spin-orbit pseudopotentials are used in the perturbational treatment of the g-tensors. This approach is shown to provide results in good agreeme nt with the all-electron treatment, at moderate computational cost. Due to the atomic nature of both mean-field all-electron and pseudopotential spin- orbit operators used, the two approaches may even be combined in one calcul ation. The atomic character of the spin-orbit operators may also be used to analyze the contributions of certain atoms to the paramagnetic terms of th e g-tensors. The new methods have been applied to a wide variety of species , including small main group systems, aromatic radicals, as well as transit ion metal complexes.