Abstract
The optical absorption and EPR spectra of Ni2+-VAg centres in the AgCl:Ni2+ and AgBr:Ni2+ systems have been investigated theoretically on the basis of the complete energy matrices including the electron–electron repulsion interaction, the ligand field interaction, the spin–orbit coupling interaction, and Zeeman interaction. Because the charge compensation forms a silver ion vacancy (VAg) which makes the attractive force acted on the each ligand ion different, it was determined that the Ni–X (X = Cl, Br) distance next to VAg is shorter than others for both AgCl:Ni2+ and AgBr:Ni2+ systems in the tetragonal symmetry. Besides, it was found that the local lattice structure of (NiX6)4− clusters in AgCl and AgBr crystals exhibit a compression distortion. This compression distortion may be ascribed to the fact that the Ni2+ ion has a smaller ionic radius and more effective charge than the Ag+ ion.
Published Version
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