New hypothetical carbon allotropes of remarkable stability estimated by MNDO solid-state SCF computations

Abstract

A new family of yet unknown carbon modifications has been proposed. The underlying building principle consists of connecting triptycyl moieties by benzene rings in two dimensions so that 2D hexagonal nets (with regular or irregular hexagons) emerge and then connecting identical nets by simple bonds. The resulting infinite structures can be described as a mixture of sp3 and sp2 carbons and are of hexagonal nature. Some of the allotropes are crystalline, but most of these 3D solids possess only a translational symmetry in one dimension. An attempt to estimate their stability by modified neglect of diatomic overlap solid-state calculations revealed that the stability of these allotropes is comparable to that of diamond.Carbon does exist in several allotropic forms1 out of which and C70 are the most recent representatives.2•3 C60 had been

Electronic structure and mechanical stability of the graphitic honeycomb lattice

“…The GH of size 0.5 in our convention is actually hexagonal diamond in which all atoms form sp 3 bonding. The results for the electronic structure of the previous calculation 3 differ significantly from ours in that the GH of size 1 or size 3 has a band gap that is greater than 5 eV. The magnitude of the band gap of the size 2 GH has also been overestimated compared with the present calculation.…”

“…We call this a graphitic honeycomb ͑GH͒ lattice in this paper. Although there was an integral number of fused benzene rings between two triptycyl moieties in the original suggestion, 3 we study below the cases where the width of the interconnected graphitic strip is a multiple of half the number of benzene rings as well. Since the family of GH's has a hexagonal array of pores along one direction, they have potential applicability as one-dimensional ionic conductors for batteries, shape-selective catalysts, molecular sieves and absorbents, and electron emitters.…”

“…The same structure has recently been suggested again by Jones. 4 In this structure, graphitic strips are interconnected via sp 3 bonds at the junctions. When the widths of the constituent graphitic strips are all identical, the structure can be regarded as a honeycomb lattice with each side ͑line segment͒ of the hexagon composed of a graphitic strip perpendicular to the lattice plane.…”

“…Carbon forms stable crystals of sp 3 or sp 2 hybrid orbitals under ambient conditions. Among the crystals of pure sp 3 bonding are cubic diamond, hexagonal diamond, and the fourfold-coordinated metastable BC-8 structure.…”

“…Among the crystals of pure sp 3 bonding are cubic diamond, hexagonal diamond, and the fourfold-coordinated metastable BC-8 structure.…”