By means of HRXRD, deviations form the ideal crystal structure are investigated. For this purpose the position and the width of X-ray reexes are measured by registering the scattered X-ray intensity while rotating the sample around an Euler angle or changing the detector position and thus varying the length and the direction of the scattering vector. In gure 18 the scattering geometry for a symmetrical and assymertical reex is shown together with the scan directions of a 2θ-Ω- and a Ω- scan.