“…Various paramagnetic centres introduced, for EPR studies, into cubic fluorite type crystal structures (CaF 2 , CdF 2 , SrF 2 , BaF 2 , SrCl 2 ) substitute divalent host metals (such as Cu 2+ , Ag 2+ , Ni + , Cr 2+ , Cr 3+ [1][2][3][4][5][6][7][8]; Sc 2+ , La 2+ [9]; atomic hydrogen H 0 [10,11]) or occupy anionic sites (like O − or OH − ) [12,13]. The transition metal ion behaviour in fluorite structures prior to 1980 has been reviewed in [14].…”