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.