Dynamical thermal diffuse scattering of fast electrons in rutile

Abstract

An n -beam dynamical Bloch wave formulation for an Einstein model of thermal diffuse scattering (TDS) is used to compare the detail of diffuse scattering patterns of 100 keV electrons from rutile with theory. Dynamically enhanced coupling or decoupling for the elastic to inelastic state transition is shown to result in the formation of Kikuchi bands, with a central deficit region which is characteristic of TDS. The symmetry of these patterns is shown to be directly related to the projection sym­metry of the crystal structure around each localized source of diffuse scattering within the unit cell. For crystal orientations where correlated phonon scattering does not dominate, good agreement between theory and experiment occurs. It is also shown how a plot of current density against orientation is useful in determining those orientations where fast electron current density is peaked at a specific site within the crystal.

Effects of multiple elastic and inelastic scattering on energy-resolved contrast in Kikuchi diffraction

“…For scattering angles larger than q 1 2 , incoherent quasi-elastic scattering is more probable, while for lower angles, diffraction via coherent forward-scattering is dominant. We now assume that one can calculate the total cross section s tot quasi of quasi-elastic, incoherent scattering from an atom in a crystal by replacing the lower limit of the integration in equation An alternative way to define s tot quasi is to weight the cross section by the incoherent fraction, similarly as done by Wang [15] and Rossouw and Bursill [16] in the description of the mean free path for thermal diffuse scattering: The mean-free-path between quasi-elastic, incoherent collisions is given by:…”