from Eq. ( ). This rather trivial fact has, however, a very large importance as it allows for DFT-type calculations of various molecular properties that are derived from the spin density, e.g. hyperfine coupling constants, with potentially higher quality than those from conventional KS-DFT. The higher quality of FDE-diab spin densities compared to those of conventional KS-DFT was already validated in previous work . Whether this also holds for spin density derived properties remains to be tested.