The influence of thermal diffuse scattering, secondary extinction and crystallite size distribution on X-ray line profiles

A method is given for correcting the integral intensities of X-ray reflexions from platelets of single crystals or powders for secondary extinction and thermal diffuse scattering (TDS). The line profiles are calculated as folding integrals from theoretical functions considering the crystallite size distribution, the total absorption, and TDS. By means of variation of the unknown parameters (fraction of TDS to the overall intensity, mean crystallite size and their polydispersity, and absorption coefficient, secondary extinction included) the calculated function has to fit the measured line profile. A detailed description of this method according to Bradaczek and Hosemann is given after introducing some modifications such as collimation errors of the primary beam and anisotropy of the lattice vibrations. The method is applied to measured line profiles of NaCl and LiF single crystals.