Binary Inorganic Crystalline Compounds

In this section the structures of binary crystal compounds are considered, including those which contain metal or non-metal atoms of different types. The limited volume of the book does not allow to pay attention to stmctures of inter-metallic compounds (see reviews [81, 82]) and of metal-rich compounds, which are in detail discussed by Rao [83] andFranzen [84]. 

In structures of inorganic crystalline compounds, coordination numbers (Nc) vary from 2 up to 12. Here and further by Nc we mean the number of atoms coordinated around the central metal atom the Nc of non-metals in MnXm structures is equal to Nc(M)n/m. In solid compounds with a framework lattice, the Nc multiplied by the ligand valence (vx) always exceeds the valence of the metal  

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The three stages of bond formation are not present in all compounds. Binary compounds like NaCl (18189) only show the second stage, the stage which all materials must undergo when they solidify. Since inorganic compounds can only be characterized by the structures of their crystalline solids, the second stage determines which compounds can exist. 

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