How good is a structure

8 Diffraction by single crystals interpretation of results 10.8.1 How good is a structure  

We have now solved and refined our structure, or we have seen a crystal structure reported in a scientific paper or a database. But what does it mean How reliable is it  

Within the same structure, some parameters will be better determined than others. The positions of heavy atoms are described more accurately than those of light ones because they have more electrons and their electronic core orbitals are less deformed, all of which improves the interaction with the X-rays. As atom movements in both molecular and lattice vibrations are dependent on their mass (Sections 8.8.2 and 8.8.4), 

Structure of the carbyne aluminum-samarium complex [ cyclo-(CyNCH2)3 Sm C(AlMe3)3 ] (Cy = cyclohexyl) containing atoms from four different periods of the periodic table, with associated structure parameters, whose standard deviations reflect more precise definition of the more electron-rich atoms. Adapted with permission from [1]. Copyright 2010 John Wiley Sons. 

Structure of the (3 phase of white phosphoms determined at — 185 C by X-ray diffraction, (a) The unit cell, viewed along the a axis, (b) The asymmetric unit with three independent P4 molecules, (c) List of 18 P—P distances (in A), showing that the spread of values is much larger than the standard deviations. Adapted from [34]. Copyright 1997 Wiley-VCH Verlag GmbH Co. KGaA. 

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