NBO analyses were performed mainly with spin-unrestricted scalar relativistic DFT calculations. With the chosen type of PBE-based hybrid exchange-correlation (XC) functional, the exchange component mixes a fraction x of Hartree-Fock exchange-i.e., the 'pure eX' functional for a single Slater determinant evaluated with the Kohn-Sham orbitals-with (1 -x) times the DFT exchange. In self-consistent DFT calculations, the XC potential and the orbitals are determined with a corresponding fraction x of eX, and the energy functional is evaluated with the resulting density. The value of x = 1/4 = 25% in the widely applied PBE0 functional parametrization can be justified based on the adiabatic connection scheme; for details, see Reference 61.