DETERMINATION OF CATION DISTRIBUTIONS BY ANOMALOUS-DISPERSION

A two-wavelength method for the distinction of elements of similar atomic numbers in generally solved crystal structures, called delta-synthesis, and its application to structures with no center of symmetry is discussed. As an example the determination of the distribution of copper and nickel in the mineral muckeite (CuNiBiS3) is presented. Copper occupies a tetrahedrally coordinated and nickel a tetragonal planar coordinated site. During these studies delta-synthesis proved to be a method which is very robust against specimen-dependent errors of measurement.