We report an exceptionally stable honeycomb carbon allotrope obtained by deposition of vacuum-sublimated graphite. The allotrope structures are derived from our low temperature electron diffraction and electron microscopy data. These structures can be both periodic and random and are built exclusively from sp^{2}-bonded carbon atoms, and may be considered as three-dimensional graphene. They demonstrate high levels of physical absorption of various gases unattainable in other carbon forms such as fullerites or nanotubes. These honeycomb structures can be used not only for storage of various gases and liquids but also as a matrix for new composites.

Recently synthesized graphitic honeycomb structures, consisting of sp 2-bonded graphene nanoribbons connected by sp 3-bonded "hinges" are investigated theoretically. Honeycombs of different "wall-chiralities" (armchair and zigzag) and sizes are studied. Simulation of the reconstruction of the hinges shows that zigzag honeycombs spontaneously rearrange, resulting in a new structure. Elastic mechanical simulations show that the Young's modulus of the structures is determined solely by the density of the hinges, regardless of the structural orientation or regularity. Compression tests display a distinct behavior of self-localized deformation, similar to that of macroscopic honeycombs. Interestingly, the failure strain of the honeycomb structure is affected significantly by its lattice size and geometrical regularity. Electronic band structures of different types of honeycombs are calculated, showing that the conductivity of armchair honeycombs follows the well-known "3n"-dependency, while zigzag honeycombs are always metallic.

This corrects the article DOI: 10.1103/PhysRevLett.116.055501.

Macroscopic samples (volume approximately cm(3), atomic density approximately 10(19) -10(20) cm(-3)) of noble-gas nanoclusters (size approximately 5-6 nm) were produced in superfluid helium by an impurity-helium gas injection technique. X-ray diffraction measurements show that the samples consist of weakly interacting nanoclusters with fivefold symmetry, such as icosahedra and decahedra. These results open new opportunities for fundamental research of nanoclusters of noble gases and other materials in well-controlled environments using experimental techniques requiring bulk samples.

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