The analysis of single-crystal Bragg reflections from profile measurements

A method is described for finding the peak limits of a Bragg reflection from an analysis of its profile. A `window' of ± 0.67σ[φ)(x)] is set up on each ordinate φ(x) in the tails of the profile and the pattern of the following ordinates is observed through the window. As the ordinate moves from the peak to the background the pattern changes and the limits of the peak may be recognized. Bragg reflections from three crystals have been analysed by this method and the limits found were generally wider than those determined by the method of Lehmann & Larsen [Acta Cryst. (1974), A30, 580–584] applied to the same data. The value of σ(I)/I was near the minimum and similar to the value from the corrected Lehmann–Larsen limits. The behaviour of the methods is also compared by representing the reflections by equivalent Gaussian profiles, and it is found that >99% of the Gaussian peak is within the limits found by the present method.