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In this paper, the optical spectra and their pressure dependence for ZnS:Ni2+ crystal have been calculated by diagonalizing the energy matrixes (including the spin-orbit coupling coefficient) based on a modified crystal-held theory, in which the normalization parameters N-t, N-e for describing covalency and the spin-orbit coupling coefficients zeta(tt), zeta(te) are obtained from a cluster approach. The calculated optical spectra and their pressure dependence show good agreement with the experimental values given by Schotz et al. (J. Phys.: Condens. Matter. 7 (1995) 795). The assignments of energy levels A(1)-(1)A(1)((1)G) and T-2-T-1(2)((1)G) are opposite to those obtained from the conventional crystal-field theory in the paper of Schotz et al. The difficulty in explaining the pressure dependence of the two energy levels is therefore removed. (C) 1999 Elsevier Science B.V. All rights reserved.