Instability of monovalent ions of transitional metals in alkaline earth fluorides: CaF2 and SrF2 activated by Co2+ or Ni2+

Аннотация

The ground state of monovalent ions of transitional metals in alkaline-earth fluorides is localized in the conduction band. It is shown by the example of monovalent Co and Ni ions in CaF₂ and SrF₂ crystals that this is responsible for the unstable state of these ions in cubic environments. A stable state is achieved by the monovalent ions shifting to off-center positions.