Calculated properties of polybenzene and hyperdiamond.

Ab initio pseudopotential calculations have been performed on two predicted metastable phases of carbon, ${\mathrm{C}}_{24}$ or polybenzene, and (${\mathrm{C}}_{28}$${)}_{2}$ or hyperdiamond. We report cohesive energies, lattice constants, bond lengths and angles, bulk moduli, and energy gaps.