Correlation symmetry analysis of electron nanodiffraction from amorphous materials

• Published in: Ultramicroscopy 2022-01, Vol.232, p.113405-113405, Article 113405
• Main Authors: Huang, Shuoyuan, Francis, Carter, Ketkaew, Jittisa, Schroers, Jan, Voyles, Paul M.
• Format: Article
• Language: English
• Subjects: Amorphous structure; Correlation symmetry analysis; Electron nanodiffraction; Rotational symmetry
• ISSN: 0304-3991; 1879-2723
• DOI: 10.1016/j.ultramic.2021.113405

•Symmetry coefficients are a method to assess rotational symmetries in nanodiffraction from amorphous materials.•Symmetry coefficients are a robust, reliable measure of atomic symmetries that is less prone to artifacts than other methods.•Example applications of symmetry coefficients are provided for simulated and experimental electron nanodiffraction from metallic glasses. Angular symmetry in diffraction reflects rotational symmetry in the sample. We introduce the angular symmetry coefficient as a method to extract local symmetry information from electron nanodiffraction patterns of amorphous materials. Symmetry coefficients are the average of the angular autocorrelation function at the characteristic angles of a particular rotational symmetry. The symmetry coefficients avoid non-structural features arising from Fourier transformation and Friedel symmetry breakdown that affect the angular power spectrum approach to determining angular symmetries in amorphous nanodiffraction. Both methods require thin samples to avoid overlapping diffraction from clusters of atoms separated in the thickness of the sample, but symmetry coefficients are more forgiving. Electron nanodiffraction experiments on a Pd-based metallic glass sample demonstrate both potentially misleading information in angular power spectrum and the utility of symmetry coefficients.