Design of a Class of New sp 2 – sp 3 Carbons Constructed by Graphite and Diamond Building Blocks

The sp 2 – sp 3 -hybridized carbon allotropes with the advantage of two hybrid structures possess rich and fascinating electronic and mechanical properties and they have received long-standing attention. We design a class of versatile sp 2 – sp 3 carbons composed of graphite and diamond structural units with variable sizes. This class of sp 2 – sp 3 carbons is energetically more favorable than graphite under high pressure, and their mechanical and dynamical stabilities are further confirmed at ambient pressure. The calculations of band structure and mechanical properties indicate that this class of sp 2 – sp 3 carbons not only exhibits peculiar electronic characteristics adjusted from semiconducting to metallic nature but also presents excellent mechanical characteristics, such as superhigh hardness and high ductility. These sp 2 – sp 3 carbons have desirable properties across a broad range of potential applications.