The analysis of a crystal structure

The first crystal structures determined in the beginning of the last century could readily be interpreted as close packing of hard spheres, and this is also how wc encounter the solid state in most contemporary textbooks. This is undoubtedly a good working model, as it reproduces many experimental data and can be used in the design of new solid phases of ionic compounds. 

However, it has been pointed out that the success of this method in reproducing experimental data cannot be taken as universal proof of its physical correctness. The lattice enthalpies of lithium metal can, for example, be calculated by modelling this material as small Li cations surrounded by large, close packed Li anions, and the agreement with experiment is good, althoi most people would consider Li(s) a metal, not a salt [24]. 

When the structures of larger molecular compounds came within reach, focus was on the connectivity and geometries of these individual components. 

Interactions with neighbouring molecules such as hydrogen bonds and jr-interactions were of course readily identified, but the overall structure often interpreted in terms of crystal packing , the underlying assumption being some kind of close packing of rather irregular objects. 

However, relatively early on in the 1950 s, some people, among them Alexander F, Wells at Imperial Chemical Industries Ltd. in the UK, realised that 

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Figure 1 shows the crystallographic flow diagram for the analysis of a crystal structure, which has an experimental part and an analytical part. More detailed explanations are given by Nyburg and Stout and Jensen. ... 

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