Efficient solution of particle shape functions for the analysis of powder total scattering data. Issue 2 (18th March 2022)

• Record Type: Journal Article
• Authors: Leonardi, Alberto; Neder, Reinhard; Engel, Michael
• Is Part Of: Journal of applied crystallography. Volume 55:Issue 2(2022)
• Page Start: 329
• Page End: 339
• Publication Date: 2022-03-18
• Subjects: shape functions -- small‐angle scattering -- total scattering -- pair distribution functions -- common volume functions; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576722001261
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : Particle shape functions are necessary to model powder scattering data that are in the form of intensity profiles and pair distribution functions. Here, an efficient method is presented to compute particle shape functions by orientational averaging of common volume functions. Contributions from particle size and size dispersity are accounted for via scaling and convolution. Abstract : Structural characterization of powder samples via total scattering methods, in either real or reciprocal space, must take into account the effect of particle shape. Here, the shape contribution of a set of ideally isolated particles to the small‐angle scattering (SAS) component of the intensity profile is modelled using the shape function [Svergun & Koch (2003). Rep. Prog. Phys. 66, 1735–1782]. The shape function is obtained by orientational averaging of common volume functions (CVFs) for a discrete set of directions. The effects of particle size and size dispersity are accounted for via scaling of the CVFs and their convolution with the underlying probability distribution. The method is applied to shapes with CVFs expressed analytically or by using discrete tables. The accurate calculation of SAS particle shape contributions up to large momentum transfer demonstrates the reliability and flexibility of modelling shape functions from sets of CVFs. The algorithm presented here is computationally efficient and can be directly incorporated into existing routines for analysis of powder total scattering data.