Electric-field gradients in ionic gadolinium compounds

Abstract
The calculation of the electric-field gradients (EFGs) in a number of ionic gadolinium compounds is considered. The lattice EFGs at the sites of Gd3+ ions have been evaluated by means of a point-charge model. Comparison of the results with quadrupole-splitting data yields a value of -75+or-2 for the Sternheimer antishielding factor gamma infinity for the Gd3+ ion. The accuracy of the lattice EFGs is discussed in terms of uncertainties in the structural parameters, the assumption of complete ionicity and the omission of ionic polarisabilities.