Roles of nitrogen substitution and surface reconstruction in stabilizing nonpassivated single-layer diamond

The existence of single-layer diamond or diamane, which could adopt the properties of its bulk counterpart, has been verified by previous calculations and experiments. Even though, carbon atoms on the top and bottom surfaces need to form dangling bonds with atoms and/or molecules to stabilize their sp(3) hybridization. In this paper, diamane is substituted by N atoms assisting the diamondlike structure to be stabilize without any passivation studied by ab initio calculation. One-fourth of N substitution on diamane, vertically stacking as NCCC, is found to be stable by surface reconstruction forming a Pandey pi-chain structure and has an antiferromagnetic property. Half nitrogen substitution on diamane, vertically stacking as NCCN, can be stable and prevails the diamane form. Its elastic constants yield high values, for example, its C-11 is as twice as diamond and its C-33 is only 21% lower than diamond. The NCCN phase is a metastable phase at 10 GPa compared with other layered carbon nitride phases showing the possible pathway to be created.