Modelling of Bragg intensity profiles. 2. Allowance for thermal diffuse scattering

A method for empirical determination of TDS (thermal diffuse scattering) corrections in X-ray structure analysis is developed. Thermal diffuse scattering is introduced into the model suggested earlier [Chulichkov et al. (1987). Sov. Phys. Crystallogr. 32, 649-653; Laktionov, Chulichkov, Chulichkova, Fetisov, Pyt'ev & Aslanov (1989). J. Appl. Cryst. 22, 315-320] for measuring the Bragg reflection intensity profile with a four-circle diffractometer. The improved model in combination with the mathematical reduction method enables the extraction of TDS and background intensity values from the experimental intensity profile. Thus the problem of TDS correction in crystal structure refinement is solved without knowledge of the sample's elasticity constants. The comparison of TDS corrections obtained by this method with those calculated from elasticity constants for hexamethylenetetramine, C₆H₂N₄, and sulfur, S₈, crystals shows good agreement.