Crystal Structure Analysis and Refinement Using Integrated Intensities from Accurate Profile Fits

摘要

Careful experimental techniques, especially using synchrotron radiation facilities, give well resolved diffraction patterns. Remaining overlapping peaks can be separated by profile fitting and profile analysis. The derived parameters are: peak position for lattice constants, integrated intensities for crystal structure work and halfwidth for line broadening analysis. Crystal structure refinements with the powder least squares program POWLS yield R factors routinely around R = 1·5% and as low as R = 0·6%. For actual structure analysis Fourier maps have been calculated in the case of the orthorhombic olivine analogue Mg2Ge04. Another non-trivial example concerns Ce02, where chemical bonding features are derived. From an analysis of anomalous dispersion in Yb20 3 the correction terms f' have been derived as a function of energy for four wavelengths measured close to the L-absorption edge of Yb.