DETERMINATION OF CRYSTAL-STRUCTURES FROM POWDER DIFFRACTION DATA BY DIRECT-METHODS - EXTRACTION OF INTEGRATED-INTENSITIES FROM PARTIALLY OVERLAPPING BRAGG-REFLECTIONS

The development of direct methods for solving crystal structures from powder diffraction data constitutes a very active research field. The basic requirement for the success of direct methods is that enough int egrated intensities can be extracted from the powder pattern. One of t he most efficient extraction methods is the two-stage Le Bail method i n which the integrated intensities and the profile parameters are refi ned separately. In this paper, a new recursive formula for the estimat ion of the integrated intensities of partially overlapping peaks, usin g the same philosophy as the Le Bail method, is derived. It is extreme ly robust, allowing to introduce zero valued initial estimates of the integrated intensities. The practical application of the procedure is discussed on the basis of two representative test examples.