Compounds Use of Crystal Chemical Knowledge

The derivative structure method, either explicitly or implicitly, has been responsible for the discovery of a number of new phases and structures of valence compounds and of metallic phases generally, the group of phases with the CdAl2S4 structure providing a good example. 

Predictions of the existence of ionic compounds and the type of structure that they may adopt are based on valence, electronegativity difference, and radius ratio of the component atoms. 

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