Superhard sp2–sp3 hybrid carbon allotropes with tunable electronic properties

Abstract

Four sp2–sp3 hybrid carbon allotropes are proposed on the basis of first principles calculations. These four carbon allotropes are energetically more favorable than graphite under suitable pressure conditions. They can be assembled from graphite through intralayer wrinkling and interlayer buckling, which is similar to the formation of diamond from graphite. For one of the sp2–sp3 hybrid carbon allotropes, mC24, the electron diffraction patterns match these of i-carbon, which is synthesized from shock-compressed graphite (H. Hirai and K. Kondo, Science, 1991, 253, 772). The allotropes exhibit tunable electronic characteristics from metallic to semiconductive with band gaps comparable to those of silicon allotropes. They are all superhard materials with Vickers hardness values comparable to that of cubic BN. The sp2–sp3 hybrid carbon allotroes are promising materials for photovoltaic electronic devices, and abrasive and grinding tools.

Three-dimensional honeycomb carbon: Junction line distortion and novel emergent fermions

“…Figure 3 shows the calculated total energy versus volume per atom for hC28 compared to other carbon phases, including S1 [40] , S2 [12] , oC16 [60] , 3D-C5 [21] , bco-C16 [61] , graphite, M-carbon [62] , and diamond. Among them, diamond is in an all-sp 3 bonding network, hC28, S2 and oC16 carbon are in a mixed sp 2 -sp 3 bonding network, and the other carbon structures are all-sp 2 bonding networks.…”

Study of Electronic Structure, Thermal Conductivity, Elastic and Optical Properties of α, β, γ-Graphyne

“…Usually, carbon materials’ dimensionality depends on its hybridization [ 15 ]. For example, sp 2 hybridization leads to 2D graphene, while sp and sp 3 hybridization form 1D and 3D carbon materials, respectively [ 16 , 17 ]. However, graphyne is found to be the only 2D carbon material so far that has both sp and sp 2 hybridization [ 18 ], which gives rise to its versatile and flexible crystal structures.…”

Interpenetrating graphene networks: Three-dimensional node-line semimetals with massive negative linear compressibilities

“…Multiple carbon crystals with mixed sp 2 and sp 3 hybridization have been proposed over the past decades [2][3][4][5][6][7][8] , although none of them have been convincingly confirmed by experiments.…”