The effective bond charge q eff , as determined from experimental values of the third-order optical susceptibility in alkali halides, is analyzed. The correlations of q eff with the ratio of the cation to anion radius, lattice constant and Szigeti effective charge are taken into account. The relationships between q eff and other parameters describing the ionicity show that the magnitude of q eff can be considered as one more parameter related to the ionicity of the crystals.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.