Fig. 1: Spin density contours in two spin qubit systems.

a, b Structures and spin densities of the negatively-charged nitrogen-vacancy center in diamond (a) and the axial kk-divacancy in 4H–SiC (b). In both systems, the spin density is localized around the carbon atoms with dangling bonds. By only treating a few atoms at the all-electron (AE) level, and the remaining using the pseudopotential (PP) approximation, an accurate prediction of spin Hamiltonian parameters can be achieved.