Calculation formulae, based upon a cluster approach, were established for the electron paramagnetic resonance g-factors, g||, g, and hyperfine structure constants, A||, A, of 3d7 ions in tetragonal octahedral crystal fields. In these formulae, parameters related to configuration interactions and covalency effects could be deduced from the optical spectra and structural parameters of a given system. The core polarization constant was the only adjustable parameter used for the calculation of A|| and A. Using the formulae, electron paramagnetic resonance parameters (g||, g, A||, A) for tetragonal Co2+-VAg centers were satisfactorily explained by considering the tetragonal distortion (displacement of the intervening Cl− ion towards the Co2+ ion along the C4-axis). The local geometry of the Co2+-VAg center was thus obtained. The electron paramagnetic resonance parameters, g and A, for the cubic Co2+ center were also deduced, from the above formulae, for the case where the tetragonal distortion was zero.

Investigations of the g Factors and Hyperfine Structure Constants for Tetragonal and Cubic Co2+ Centers in AgCl Crystals. S.Y.Wu, W.C.Zheng, P.Ren: Physica B, 2000, 292[3-4], 337-43