Theoretical studies of EPR parameters and microstructure of the rhombic Co2+-V-Ag centre in AgCl

The perturbation formulae of EPR g-factors g(i) (i = x, y, z) and hyperfine constants Ai for a 3d(7) (Co2+) ion at a rhombic octahedral site in a crys tal are established from a cluster approach. In these formulae, the contrib utions from the covalency effect, the configuration interaction and the rho mbic crystal field are considered and the parameters used in the calculatio n of EPR parameters. except the core polarization constant x in the calcula tion of Al, can be estimated from the optical spectra and the structure dat a of the studied system. From these formulae, the EPR parameters g(i) and A (i) for the rhombic Co2+-V-Ag centre in AgCl are reasonably explained by co nsidering suitable rhombic distortion and so the microstructure of this rho mbic centre is obtained.