Predicted new low energy forms of carbon

We have used a first-principles molecular-dynamics technique to find the relaxed atomic geometries and the corresponding electronic structures of three of the simplest novel forms of three-coordinated solid carbon. We compare the energies of these structures to those of graphite and of the icosahedral fullerene ${\mathrm{C}}_{60}$. All of these forms of carbon contain only one kind of carbon atom. One of these, which we name polybenzene, is found to have a substantially lower energy per atom (0.23 eV) than ${\mathrm{C}}_{60}$, yet contains only 24 atoms per unit cell.