Approximations of the dynamical theory of diffraction contrast

Abstract
The approximations of diffraction contrast theory, in particular the two-beam approximation and the column approximation, are critically examined. Contrast calculations for dislocations, spherically symmetric coherency strains and magnetic domain walls are described. In most cases the effect of the column approximation is small. This is because θD, the half angle of divergence of the energy flow in the crystal is usually very much less than θB, the Bragg angle. The results are discussed in terms of a perturbation theory of scattering which may prove useful for the determination of the structure of small, unknown defects.

This publication has 17 references indexed in Scilit: