title: Interpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimens.
abstract: The interpretation of angular symmetries in electron nanodiffraction patterns from thin amorphous specimens is examined. It is found that in general there are odd symmetries in experimental electron nanodiffraction patterns. Using simulation, it is demonstrated that this effect can be attributed to dynamical scattering, rather than other divergences from the ideal experimental conditions such as probe-forming lens aberrations and camera noise. The departure of opposing diffracted intensities from Friedel's law in the phase grating formalism is calculated using a general structure factor for disordered materials. On the basis of this, a simple correction procedure is suggested to recover the kinematical angular symmetries, and thus readily interpretable information that reflects the symmetries of the original projected object. This correction is numerically tested using both the phase object and multislice calculations, and is demonstrated to fully recover all the kinematical diffracted symmetries from a simulated atomic model of a metallic glass.
authors: Monash Centre for Electron Microscopy and School of Physics, Monash University, Clayton, Victoria, 3800, Australia.
authors: Amelia C Y
authors: AC
authors: Liu
authors: Australian Nuclear Science and Technology Organization, Lucas Heights, New South Wales, 2234, Australia.
authors: Gregory R
authors: GR
authors: Lumpkin
authors: School of Physics and Astronomy, Monash University, Clayton, Victoria, 3800, Australia.
authors: Timothy C
authors: TC
authors: Petersen
authors: Department of Materials Science and Engineering and Monash Centre for Electron Microscopy, Monash University, Clayton, Victoria, 3800, Australia.
authors: Joanne
authors: J
authors: Etheridge
authors: Department of Materials Science and Engineering and Monash Centre for Electron Microscopy, Monash University, Clayton, Victoria, 3800, Australia.
authors: Laure
authors: L
authors: Bourgeois
keywords: Friedel symmetry; amorphous materials; electron nanodiffraction; scanning transmission electon microscopy; short-range order