What Information Can Be Obtained and How Reliable Is It

Crystal structure determination requires the development of a suitable model for periodic electron density distribution in the crystal that is related by Fourier transform to the structure factors that can be derived from the experimentally measured diffraction intensities. The model, in practice, is atomistic and consists of coordinates and atom types for all symmetry independent atoms as well as parameters that are used to describe the (mean square amplitude of) displacement of the atoms about their mean positions, which arises due to molecular motions and small variations in the mean position across the collection of unit cells that comprise the crystal. 

A complete structure determination of course reveals the chemical composition of the crystal studied, but most importantly it provides accurate geometric information. This includes bond lengths, bond angles, torsion angles, interplanar 

In the context of crystal engineering, rather than the use of crystallography for molecular structure determination, single crystal diffraction is often vital for establishing chemical composition. It is then intermolecular interactions, supra-molecular synthons, network topology or perhaps pore or cavity dimensions rather than intramolecular geometries that are the most important results derived form a crystal structure determination. However, the latter should of course always be checked as part of the overall assessment of quality of the structure determination.. 

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