Refinement of free structure parameters of a thin film when only one reflection is available

A procedure is described to exploit measurements for the refinement of free structure parameters if only a few (or even only one) reflections are avai lable. The method is illustrated taking an epitaxial layer of Ga0.5In0.5P d eposited on (001)GaAs as an example, where the number of accessible reflect ions is limited by geometrical conditions. Another complication with this m aterial arises from the well known ordering phenomenon, which occurred in a small part of the layer only It is shown that the energy dependence of DAF S (diffraction anomalous fine structure) intensity is still sufficiently se nsitive to values of free structure parameters when the oscillating part of the DAFS/XAFS (X-ray absorption fine structure) structure factor is ignore d for evaluation of intensity. This facilitates evaluation of DAFS intensit ies considerably by avoiding time-consuming analysis of fine structure. (C) 2000 International Union of Crystallography Printed in Great Britain - all rights reserved.