107 In this way the absolute values of the structure factors may be found, not the phases (6. 8). The problem to find these phases is the phase problem. The present article will treat the following topics. At first the description of the ideal crystal will be given in Chap. B. The underlying principles of this description are the concepts of reciprocal lattice, FOURIER synthesis and sym- metry. The evaluation of the intensity will then follow in Chap. C and D. Chap. E is concerned with the phase problem and related topics. Though this article treats the analysis of crystal structures, the...