Multislice calculation of Kikuchi patterns

The diffraction of the inelastically and pseudo-elastically scattered electrons in a crystal gives rise to the diffuse background in a diffraction pattern, including Kikuchi patterns as they are known, which are very sensitive to the direction of electron incidence relative to the crystal orientation. In the exact zone orientation, i.e., when the electrons are travelling along a major zone axis, a Kikuchi-band pattern is formed which reflects the crystal symmetry about that axis; otherwise, the pattern is known as Kikuchi-line pattern (thereafter collectively referred to as K-patterns).For localized inelastic events, such as interactions of incident electrons with shell electrons and various crystal point defects, in which intra-process coherence is negligible, the K-patterns can be simulated using the method described below.An inelastic event creates a spherical wave which, however, is strongly peaked in the forward direction of electron traveling, as given by the typical form f(θ)e-kr/r, where symbols have their usual meanings.

Inelastic Scattering and Electron Spectroscopy

The reasons for studying energy losses can be quite different. The motivations are often highly diversified even if searchers are electron microscopists For instance, the problem of useful penetration involves studying the question of chromatic blurring even if in many cases this effect is not sufficient for explaining the limitations in penetration. The formation of damage (direct knock-on and ionization) is interesting in many ways. In electron microscopy an important point is also the contrast preservation in an inelastic event. This point is related to the useful penetratior (principally in crystalline materials). If that is rather well understood in the case of potentials which are not localized (1) (plasmons and single quasi free electron excitations), it is not so clear in the case of localized interactions as electron phonon ones (2,3,4) or inner shell excitations even if the scattering angle is quite small. However the understanding of this contrast preservation is fundamental.