High-throughput calculations screening for new direct band gap superhard carbon allotropes

Abstract High-throughput first principles calculations for 109 carbon allotropes were performed. The elastic constants and phonon calculations suggest that these new structures are mechanically and dynamically stable at ambient pressure. Seven direct band gap semiconductor carbon allotropes were uncovered. The Vickers hardness of all seven structures exceeds 40 GPa, indicating that these allotropes are potential superhard materials.