Borides with Two-Dimensional Boron Networks

Existence and Crystal Chemistry of Borides 6.7.2.3. Borides with Two-Dimensional Boron Networks... 

With the exception of some special cases, two major classes of structure can be distinguished. In the first, the metal-rich borides possess boron atoms at the centers of trigonal prisms of metal atoms, and the boron atoms interact in one- or two-dimensional homonuclear networks. This class covers the range of stoichiometries from M3B to MB2. Presumably these structures, particularly those containing the highest metal-to-boron ratio, are controlled by the requirements of the metal... 

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