IUCrJ (Mar 2022)

Preferred orientation and its effects on intensity-correlation measurements

  • Jack Binns,
  • Connie Darmanin,
  • Cameron M. Kewish,
  • Sachini Kadaoluwa Pathirannahalge,
  • Peter Berntsen,
  • Patrick L. R. Adams,
  • Stefan Paporakis,
  • Daniel Wells,
  • Francisco Gian Roque,
  • Brian Abbey,
  • Gary Bryant,
  • Charlotte E. Conn,
  • Stephen T. Mudie,
  • Adrian M. Hawley,
  • Timothy M. Ryan,
  • Tamar L. Greaves,
  • Andrew V. Martin

DOI
https://doi.org/10.1107/S2052252521012422
Journal volume & issue
Vol. 9, no. 2
pp. 231 – 242

Abstract

Read online

Intensity-correlation measurements allow access to nanostructural information on a range of ordered and disordered materials beyond traditional pair-correlation methods. In real space, this information can be expressed in terms of a pair-angle distribution function (PADF) which encodes three- and four-body distances and angles. To date, correlation-based techniques have not been applied to the analysis of microstructural effects, such as preferred orientation, which are typically investigated by texture analysis. Preferred orientation is regarded as a potential source of error in intensity-correlation experiments and complicates interpretation of the results. Here, the theory of preferred orientation in intensity-correlation techniques is developed, connecting it to the established theory of texture analysis. The preferred-orientation effect is found to scale with the number of crystalline domains in the beam, surpassing the nanostructural signal when the number of domains becomes large. Experimental demonstrations are presented of the orientation-dominant and nanostructure-dominant cases using PADF analysis. The results show that even minor deviations from uniform orientation produce the strongest angular correlation signals when the number of crystalline domains in the beam is large.

Keywords