THE VALIDITY OF APPROXIMATIONS MADE IN DIFFERENTIAL ANOMALOUS X-RAY-SCATTERING

Approximations of weighting-factor functions are used when determining coordination numbers from differential anomalous scattering (DAS) exp eriments, The accuracy of two single-value approximations for the weig hting functions are tested using non-interacting hard-sphere models of systems that have been studied previously with DAS. The first approxi mation is an average of the weighting-factor function over the experim ental wave-vector range, The second is the weighting-function value at the wave vector that is related to a peak position in the correspondi ng differential radial distribution function (dRDF). It was found that the first approximation introduced up to 10% error into calculated co ordination numbers. The second weighting-factor approximation introduc ed minimal error into the coordination-number calculations and is simp le to use.