Perturbed-angular-correlation measurements of trivalent indium defects in silver chloride

The interaction of vacancies with trivalent In111 ions in AgCl was studied by the perturbed - angular-correlation (PAC) method. Measurements at 77 K showed that the In111 ions occurred predominantly in two well-defined lattice defects, characterized by electric field gradients (EFGs) having frequencies Q1=21.5 MHz and Q2=43 MHz, each having axial symmetry, and each having its largest principle axis (zz) component in 100 directions. Two possible In-vacancy complexes are proposed for defect 1. The In ion, occupying a Ag lattice site, may be bound either to a single vacancy at a next-nearest Ag (1,0,0) site, or to two vacancies occupying next-nearest Ag sites at right angles with respect to the In ion. Defect 2 is attributed to a linear In-vacancy complex in which two vacancies occupy next-nearest Ag sites on opposite sides of the substitutional In site, e.g., at (1,0,0) and (-1,0,0) sites with respect to the In ion. Calculations of EFGs arising from these configurations, using a point-charge model, agree well with the measured EFGs.