There are four main sections. The Introduction continues, after the present subsection, with a discussion of the rationale for and genesis of the Subcommittee that wrote this report (Subsection 1.2), notation for position and displacement vectors (1.3), a consideration of the structure factor and atomic displacements (1.4), and comments about the terminology to be used (1.5).
The second main section, Displacement Parameters Based on the Gaussian Approximation, concerns the kinds of parameters describing atomic displacements that have most often been used in crystal structure analysis and hence are most commonly found in the literature on the subject. Its subsections are: 2.1, Anisotropic displacement parameters, which includes a discussion of the common symbols used; 2.2, Equivalent isotropic displacement parameters; and 2.3, Graphical representations of the Gaussian mean-square displacement matrix.
The third main section, Beyond the Gaussian Approximation, considers the expressions used when the Gaussian approximation is not adequate. Our Recommendations for nomenclature are in the final main section.
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