Efficient solution of particle shape functions for the analysis of powder total scattering data

Alberto Leonardi; Reinhard Neder; Michael Engel

doi:10.1107/S1600576722001261

Efficient solution of particle shape functions for the analysis of powder total scattering data

J Appl Crystallogr. 2022 Mar 18;55(Pt 2):329-339. doi: 10.1107/S1600576722001261. eCollection 2022 Apr 1.

Authors

Alberto Leonardi¹, Reinhard Neder², Michael Engel¹

Affiliations

¹ Institute for Multiscale Simulation, IZNF, Friedrich-Alexander-Universität Erlangen-Nürnberg, Cauerstrasse 3, Erlangen, Bavaria 91058, Germany.
² Institut für Physik der Kondensierten Materie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudstrasse 3, Erlangen, Bavaria 91058, Germany.

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.

Keywords: common volume functions; pair distribution functions; shape functions; small-angle scattering; total scattering.

Grants and funding

This work was supported by the Deutsche Forschungsgemeinschaft through the Cluster of Excellence Engineering of Advanced Materials (grant No. EXC 315/2); A. Leonardi acknowledges support from the Deutsche Forschungsgemeinschaft (grant No. LE4543/2-1).