On the number of statistically independent observations in a powder diffraction pattern

When in a powder diffraction pattern two or more peaks heavily overlap, the integrated intensities of the overlapping reflections are correlated. This paper describes a method, based on the study of the peak overlap, which estimates the number of statistically independent intensities associated with a powder diagram. Such a number can be useful for forecasting the rate of success of direct-methods procedures for ab initio crystal structure solution and for evaluating a priori the efficiency of least-squares programs devoted to crystal structure refinement.