REFINEMENT OF ATOMIC POSITIONS IN BIXBYITE OXIDES USING PERTURBED ANGULAR-CORRELATION SPECTROSCOPY

In a number of isostructural sesquioxides M2O3 (M = Sc, In, Y, Yb, Dy, Ho, Sm, Gd) with the bixbyite structure the electric field gradients at substitutional Cd-111 nuclei show a regular and smooth dependence o n the lattice constant. The electric field gradients allow the positio ns of all atoms in the unit cell to be determined with an accuracy of 0.3 pm by means of a simple point-charge model; this is typically five times better than the data available from neutron and X-ray diffracti on experiments.