Local structure and local compressibilities around Co 2+ impurity in ZnSiF 6·6H 2O crystal determined from electron paramagnetic resonance data

Abstract

The perturbation formulas of g-factors g ‖, g ⊥ and hyperfine structure constants A ‖, A ⊥ for 3d 7 ion in trigonal octahedral crystal field are established on the basis of a cluster approach. These formulas consist of the contributions from configuration interaction and covalency effect and the parameters related to both effects can be estimated from the optical spectra and the structural data of the system under study. According to these formulas, the local trigonal distortion angle β at pressure P=0 and the local compressibilities d ln β/d P in two pressure regions around Co 2+ impurity in ZnSiF 6·6H 2O crystal are estimated by fitting the calculated electron paramagnetic resonance parameters g i , A i and their pressure coefficients to the observed values. The results show that these local values are different from those of the host crystal because of the influence of impurity.