Coordination polyhedra Subject

Apart firom the unphysical nature of ionic radii, they are subject to the further criticism that they do not lead to correct predictions in mixed anion compounds such as oxyfluorides [9]. Also they do not allow one to handle correctly compounds in which there is a range of bond lengths within a given coordination polyhedron. One example of the latter is afforded by the case of B2O3 which is discussed below. 

A partial explanation for this surprising difference is provided by a combination of an analysis of the role of magnetic site coordination polyhedron in determining the electronic structure and application of the Spin Dimer Model.The octahedron about Os in Li50s06 is subject to a much stronger psuedo-tetragonal compression, 4 Os - O bonds at 1.908 A... 

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