  The formation of the magnetic moment in C- and N-doped MgO is the result of a
delicate interplay between Hund's coupling, hybridization and Jahn-Teller
distortion. The balance depends on a number of environmental variables
including electron doping. We investigate such a dependence by self-interaction
corrected density functional theory and we find that the moment formation is
robust with respect to electron doping. In contrast, the local symmetry around
the dopant is more fragile and two different geometries can be stabilized.
Crucially the magnetic moment is always extremely localized, making any carrier
mediated picture of magnetism in d^0 magnets unlikely.
