A method for the recovery of local order coefficients from two-dimensional intensity data for binary f.c.c. alloys

A method is derived which permits the Cowley-Warren order parameters to be recovered from diffuse scattering measurements made in one plane in reciprocal space for systems with only short-range correlations. The procedure is demonstrated first by application to some at-temperature measurements on Cu₃Au and then by considering some simulated diffraction profiles, with and without controlled errors. From the simulated scattering without error, an empirical rule is developed which allows one to decide if a given profile is amenable to this recovery method. By simulation of data with varying constant-background contributions, it is shown that such an error can be recognized and corrected.