On the way to carbon nitride

The available data on the problem of hypothetical crystalline carbon nitride are considered. These involve the crystal structure, the nature of chemical bonding, and physical properties of carbon nitride of which the most interesting is its predicted high hardness comparable with that of diamond. The experiments aimed at synthesising carbon nitride are described, and properties of the materials obtained are characterised. The results of thermodynamic calculations pertinent to carbon nitride and processes of its synthesis are discussed. The bibliography includes 144 references.