Solving Crystal Structures Using Several Wavelengths from Conventional Sources. Anomalous Scattering by Holmium

The anomalous scattering terms for trivalent holmium are measured for Cu Kα1, Kα2 and Kβ radiation in diffraction experiments with a crystal of HoNa(edta).8H2O. Intensities at these wavelengths and at Mo Kα are used to calculate amplitudes and the phase difference for the waves scattered by holmium and by the rest of the structure to test the multiple-wavelength method of diffraction phase determination. Relative phases are determined with a mean accuracy of 44° for 759 high-angle reflections. A similar calculation for the analogous Sm crystal using synchrotron radiation data gives the phase difference with an average error of 5°.