The structure of the primary rhodium defect in rhodium-doped AgCl was determined by EPR and electron-nuclear double-resonance technique (ENDOR) spectroscopies. The substitutional and orthorhombic ${\mathrm{Rh}}^{2+}$ complex, (${\mathrm{RhCl}}_6$${)}^{4\mathrm{-}}$, was elongated along a [100] axis with a silver ion vacancy in a next-nearest-neighbor position in the plane perpendicular to the elongation axis. The large superhyperfine interactions measured for the first-shell chloride ions and the fourth-shell silver ions along the elongation axis suggest that the complex was stabilized by covalent interactions. The structural model deduced from these experiments provided an explanation for the dynamic behavior of the complex which was observed above ∼80 K.

• Received 1 February 1988

DOI:https://doi.org/10.1103/PhysRevB.38.4343