Diamond and Diamond-Like Carbon

Abstract

Among the two long-known allotropic forms of carbon, sp2-hybridized multilamellar graphite is the thermodynamic stable form at normal temperature and pressure, whereas the denser sp3-hybridized diamond becomes favored at very high pressures. Portions of graphene sheets with dangling bonds connected with hydrogen atoms are planar polycyclic benzenoid hydrocarbons (benzenoids). Similarly, portions of the diamond lattice with dangling bonds connected with hydrogen atoms are diamond hydrocarbons (diamondoids). Dualists of benzenoids consist of vertices in the centers of benzenoid rings and of edges connecting vertices corresponding to benzenoid rings sharing CC bonds. Analogously, dualists of diamondoids consist of vertices in the centers of adamantane units and of edges connecting vertices corresponding to adamantane units sharing six-membered rings.