Abstract
Earlier work by the author and Das is extended to apply to new experimental results. The extensions over previous work include: detailed treatment of 56 neighboring ions as compared with the earlier 24, the use of the shell model, and inclusion of the crystal beyond the 56 neighbors in a continuum approximation. Comparison with experiment indicates that calculations of field gradients using a shell model are good only to within a factor of about 2. Possible reasons for the discrepancy are discussed.