DETERMINATION OF CATION DISTRIBUTIONS BY ANOMALOUS-DISPERSION

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