Hubert A J M, Römer R, Beanland R
Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
Ultramicroscopy. 2019 Mar;198:1-9. doi: 10.1016/j.ultramic.2018.12.007. Epub 2018 Dec 15.
We use semi-automated data acquisition and processing to produce digital large angle CBED (D-LACBED) patterns. We demonstrate refinements of atomic coordinates and isotropic Debye-Waller factors for well-known materials using simulations produced with a neutral, spherical independent atom model. We find that atomic coordinate refinements in AlO have sub-pm precision and accuracy. Isotropic DWFs are accurate for Cu, a simple fcc metal, but do not agree with X-ray measurements of GaAs or AlO. This lack of agreement is probably caused by bonding and change transfer between atoms. While it has long been appreciated that CBED is sensitive to bonding, examination of D-LACBED data shows that some regions exhibit large changes in diffracted intensity from small changes in the periodic crystal potential. Models of bonding will be essential to fully interpret D-LACBED data.
