The influence of an uneven surface on the diffraction pattern of a perfect crystal

A simple theoretical model is given for the diffraction of X-rays on a perfect crystal with uneven surface. It is assumed that the crystal surface can be approximated by a system of small surfaces, variously inclined from the diffraction planes, and that the diffraction can be calculated as the superposition of independent diffractions from the different small surfaces. The model was verified experimentally by measuring a perfect germanium crystal with an uneven surface on a triple-crystal diffractometer. The unevenness of the surface was studied by optical measurement. Very good agreement with theory was obtained.In conclusion the authors thank Dr. Z. Trousil for preparing the Ge single crystals and M. Prochodov and V. idová for carefully performing the numerical calculations and measurements.