In Chapter 11 we discussed why diffraction occurs; in this chapter we give a more detailed mathematical treatment. It may be more detailed than you need at this stage. Diffraction is one of those phenomena that lends itself directly to a detailed mathematical modeling, but there is a danger: don’t become so engrossed in the math that you miss the principles involved; conversely, don’t ignore the subject because it is mathematically daunting! The topic of this chapter is one which causes major problems for many microscopists. The treatment we will follow is known as the ‘dynamical theory.’ Later we will make some gross simplifications, partly because this is instructive and partly because these simplifications do apply to some important special cases; the kinematical approximation is one such simplification. Many other texts begin with the so-called ‘kinematical’ treatment and then advance to the more realistic, more general dynamical case. We will not do this but we will introduce the words and assumptions in Chapter 27.
KeywordsDirect Beam Diffract Beam Bloch Wave Total Wave Function Exit Surface
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- This treatment of diffracted beams follows that given by Hirsch and Whelan and the textbook by Hirsch et al. that built on Darwin’s treatment of X-ray diffraction.Google Scholar
- Darwin, CG 1914 Röntgen-Ray Reflection I;II Phil, Mag. 27 315–333 and 675-690. Charles Galton Darwin was a grandson of Charles Robert Darwin and, like (the) Darwin (and Hirsch), became a Fellow of Christ's College.Google Scholar
- Hecht, E 1987 Optics, 4th ed., Addison-Wesley, Reading MA.Google Scholar
- Howie, A and Whelan, MJ 1961 Diffraction Contrast of Electron Microscope Images of Crystal Lattice Defects. II The Development of a Dynamical Theory Proc. Roy. Soc. A263 217–237.Google Scholar
The Column Approximation
- Spence, JCH 2003 Experimental High-Resolution Electron Microscopy 3rd Ed. Oxford University Press New York. Uses the quantum-mechanical convention rather than the crystallographic one.Google Scholar