Intensity statistics. I

Two methods for evaluating the probability distribution of X-ray intensities are presented. The first is an exact series representation in powers of the atomic form factors. Overall thermal-displacement and scale parameters are shown to be dependent only on the ratio of intensity to σ₂. The second method is a maximum-entropy distribution based on the first two moments of the intensity distribution. It is shown to be a robust and accurate method of incorporating heavy-atom effects and results in a simple generalization of the Wilson distribution.