Structural aspects and conformation of linear carbon polytypes (carbynes)

The apparent discrepancy that an element with the richest chemistry of all should possess only few polymorphs was resolved recently by the increasing recognition of carbynes, chain-like compounds with sp-configuration and conjugated triple or cumulated double bonds between the carbon atoms in the chain. A simple classification approach is suggested leading to a linear relationship between the number of atoms in the chain and the c-axes lengths, the cell volumes, and the a0c0 ratio. Moreover, a new carbyne form was observed which may have originated from regraphitization of shock-formed diamond. The new carbon polymorph fits well in the gap between already known carbyne forms.