Amorphizing non-cubic structures of carbon. The case of rhombohedral and hexagonal crystalline supercells

We have recently developed a procedure to amorphize structures of some semiconducting elements starting from cubic supercells. This procedure includes the use of an ab initio computer code based on the Harris functional, 64 or 216 atoms in the originally crystalline supercells, and a thermal procedure that heats the samples to just below their corresponding melting temperature. Here we report the use of non-cubic supercells: the graphitic hexagonal (72 atoms) and rhombohedral (108 atoms) supercells, both with a density ρ=2.239 g/cm3. The rhombohedral form is metastable whereas the hexagonal form is stable. We find that the radial distribution functions as well as the atomic topologies are similar in both cases, indicating that the symmetry of the initial crystalline structure does not affect the final amorphized samples.