POWERFUL NEW SOFTWARE FOR THE SIMULATION OF WAXS AND SAXS DIAGRAMS

The study of poorly crystallized compounds by X-ray powder diffraction is sometimes very difficult because structural information is not easily obtained. One way to determine these structural data is to test more or less complex crystallographic models and compare simulated wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS) spectra with experimental ones. This paper presents new software for the simulation of X-ray patterns. Three modules are available; PRECRAY, SIMVAX and SIMVAX1. PRECRAY allows the definition of the structural model for the solid and different conditions for the calculation of the X-ray diagram, such as the type of anode and the angular domain. SIMVAX and SIMVAX1 calculate all the interatomic distances according to the Debye formula; the contributions of the different kinds of atoms may be displayed. Applications to different sorts of material are presented; the influences of several kinds of crystallographic defects on the X-ray diagrams have been studied. The relevance of this simulation approach to the interpretation of small-angle X-ray scattering patterns, by the generation of complex models of particles and calculation of the scattered intensity, is also presented.