Atomic coordinates table access

Fortunately, the need to amass coordinates of atoms in reported crystal structures has already been appreciated, and efficient computer-based databases are now available. As a result, it is not necessary to type large sets of numbers into a computer, because they can be derived in computer-ready form from a database. In addition to the ready access to atomic coordinate tables, there are many excellent computer-graphics, geometrical, and statistical programs available for comparisons of structures. In practice, however, it is additionally advantageous to build molecular models either of the ball-and-stick variety or the space-filling variety, if chemical or biochemical insight is required from a comparison of molecular structures observed by crystal structure analyses. 

Intermolecular coordinate interactions involving an expansion of the silicon coordination number were revealed by X-ray diffraction mainly for monosubstituted silanes of the HjSiX type, in whose molecules the central Si atom is sterically accessible. Since all the compounds of this type are gases or volatile liquids, their association was observed only at low temperatures. There are only few exceptions (Table 11). 

The periodic membership of metallic elements (see Figure 1.3), and location in the Periodic Table impacts on their chemical behaviour and reactivity. Prior to an examination of synthetic strategies, it is useful to introduce the various groups of metallic elements that act as the central atom in most coordination complexes, to identify aspects of their chemistry that impact on complexes that are accessible and the subsequent development of synthetic procedures. In general, the periodic block origins of a metal will play a part in the type of complexes that can be easily and conveniently synthesized. 

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