A new cubic superhard large-cell carbon allotrope: c-C200

Abstract

A new cubic superhard large-cell carbon allotrope with 200 carbon atoms per unit cell (named c-C200) is theoretically predicted by the unbiased swarm structure searching techniques combined with the first-principles calculations. The phonon and elastic constants calculations show that c-C200 is dynamically and mechanically stable. The calculated hardness of c-C200 is 47 GPa, which means that c-C200 is a potential superhard material. The calculated electronic band structure of c-C200 shows that it is a quasi-direct band gap semiconductor with a gap of 2.781 eV.