A bond topological approach to borate minerals: A brief review

作者：Hawthorne F C^*

来源：Physics and Chemistry of Glasses-European Journal of Glass Science and Technology Part B, 2018, 59(3): 121-129.

DOI：10.13036/17533562.59.3.023

Here I use bond topology and bond valence theory to examine the structural chemistry of borate minerals. Bond valence theory is briefly reviewed, with particular emphasis on the valence sum rule and the valence matching principle. With regard to the valence matching principle for simple cations and oxyanions, I define a Matching index: M=(Lewis acidity Lewis basicity)/Lewis basicity. Structures with large positive values of M show significant strain in the form of unusual coordination numbers for some cations, and unusual mean bond lengths for other cations. Lewis acidities of geochemically common cations are commonly smaller than Lewis basicities of common oxyanions. This mismatch drives both polymerisation and hydroxylation of oxyanions that reduce the Lewis basicities of the resulting complex oxyanions, enabling a better match with the Lewis acidities of geochemically common cations. More complicated minerals are considered as made up of a (usually anionic) structural unit and a (usually cationic) interstitial complex, and the principle of correspondence of Lewis acidity basicity (the mean field equivalent of the valence matching principle) is a powerful method for predicting many aspects of the chemical composition and stereochemistry of complicated minerals.

• 出版日期2018-6