Theoretical studies of the optical spectra and their pressure dependence for ZnS : Ni2+ crystal

In this paper, the optical spectra and their pressure dependence for ZnS:Ni 2+ crystal have been calculated by diagonalizing the energy matrixes (inclu ding the spin-orbit coupling coefficient) based on a modified crystal-held theory, in which the normalization parameters N-t, N-e for describing coval ency and the spin-orbit coupling coefficients zeta(tt), zeta(te) are obtain ed from a cluster approach. The calculated optical spectra and their pressu re dependence show good agreement with the experimental values given by Sch otz et al. (J. Phys.: Condens. Matter. 7 (1995) 795). The assignments of en ergy levels A(1)-(1)A(1)((1)G) and T-2-T-1(2)((1)G) are opposite to those o btained from the conventional crystal-field theory in the paper of Schotz e t al. The difficulty in explaining the pressure dependence of the two energ y levels is therefore removed. (C) 1999 Elsevier Science B.V. All rights re served.