Graphyne

Graphyne is an allotrope of carbon. Although it has been studied in theoretical models, it is very difficult to synthesize and only small amounts of uncertain purity have been created. Its structure is one-atom-thick planar sheets of sp and sp2-bonded carbon atoms arranged in crystal lattice. It can be seen as a lattice of benzene rings connected by acetylene bonds. The material is called graphyne-n when benzene rings are connected by n sequential acetylene molecules, and graphdiyne for a particular case of n = 2 (diacetylene links). Depending on the content of acetylene groups, graphyne can be considered a mixed hybridization, spk, where k can be 1 or 2, and thus differs from the hybridization of graphene (considered pure sp2) and diamond (pure sp3). First-principles calculations showed that periodic graphyne structures and their boron nitride analogues are stable. The calculations used phonon dispersion curves and ab-initio finite temperature, quantum mechanical molecular dynamics simulations.