Stacking stability of C2N bilayer nanosheet.

In recent years, a 2D graphene-like sheet: monolayer C2N was synthesized via a simple wet-chemical reaction. Here, we studied the stability and electronic properties of bilayer C2N. According to a previous study, a bilayer may exist in one of three highly symmetric stacking configurations, namely as AA, AB and AB'-stacking. For the AA-stacking, the top layer is directly stacked on the bottom layer. Furthermore, AB- and AB'-stacking can be obtained by shifting the top layer of AA-stacking by a/3-b/3 along zigzag direction and by a/2 along armchair direction, respectively, where a and b are translation vectors of the unit cell. By using first-principles calculations, we calculated the stability of AA, AB and AB'-stacking C2N and their electronic band structure. We found that the AB-stacking is the most favorable structure and has the highest band gap, which appeared to agree with previous study. Nevertheless, we furthermore examine the energy landscape and translation sliding barriers between stacking layers. From energy profiles, we interestingly found that the most stable positions are shifted from the high symmetry AB-stacking. In electronic band structure details, band characteristic can be modified according to the shift. The interlayer shear mode close to local minimum point was determined to be roughly 2.02 × 1012 rad/s.