Crystallography geometric

One must be sure of the purity of the model compound. It may have deteriorated (for example, by reaction or water absorption), its surface may not have the same composition as the bulk, or it may not be of the correct crystallographic phase. It is tempting to use single crystals to be sure of the geometric structure, but noncubic crystals give angle-dependent spectra. The crystallography of any compound should be checked with XRD. 

Crystallography is a very broad science, stretching from crystal-structure determination to crystal physics (especially the systematic study and mathematical analysis of anisotropy), crystal chemistry and the geometrical study of phase transitions in the solid state, and stretching to the prediction of crystal structures from first principles this last is very active nowadays and is entirely dependent on recent advances in the electron theory of solids. There is also a flourishing field of applied crystallography, encompassing such skills as the determination of preferred orientations, alias textures, in polycrystalline assemblies. It would be fair to say that... 

J.V. Smith, Geometrical and Structural Crystallography, Wiley, New York, 1982. 

Baerlocher, C., Hepp, A., and Meier, W.M. (1977) DLS-76, A Program for the Simulation of Crystal Structures hy Geometric Refinement, Institute of Crystallography and Pettography, ETH, Zurich, Switzerland. 

The spectra of other complexes with tripod ligands, such as tren and TSN, have also been studied. Their stereochemistry, forced upon them by the geometric requirements of the ligands, is probably not very different from the trigonal bipyramid. In fact X-ray crystallography has shown that the cation of the compound [Cu(NCS)tren]SCN has a distorted trigonal bipyramidal structure (46). The spectra of this compound (44) and of [CuBr(TSN)]Br (45) show the characteristic two-band shape for trigonal bipyramidal complexes. 

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