Novel two-dimensional diamond like carbon nitrides with extraordinary elasticity and thermal conductivity

In this work, two new types of structurally stable two-dimensional (2D) carbon nitrides are predicted by first-principles calculations. They are derived by extracting two adjacent atomic layers from cubic diamond or hexagonal diamond and then substituting the unsaturated C atoms with N atoms. The formed 2D diamond-like carbon nitrides are named as 2D c-C2N2 and 2D h-C2N2. First-principles calculations on their structural stability, electronic, mechanical, and thermal properties were performed. It is revealed that they are semiconductors with a direct band gap of similar to 4.43 eV for c-C2N2 and an indirect band gap of 3.70 eV for h-C2N2. Their Young's modulus reaches as high as 1.08 TGa for c-C2N2 and 1.06 TGa for h-C2N2, both of which are comparable to that of graphene. The c-C2N2 shows a thermal conductivity of 41200 W/m.K while the h-C2N2 has a thermal conductivity of 49500 W/m.K at 80 K. These values are several times of those of graphene and diamond at the same temperature. This research provides theoretic perspectives for exploring novel 2D carbon nitrides with extraordinary properties. Once experimentally realized, they would open widespread applications in electronics, optoelectronics, heat management, and mechanical structures. (C) 2018 Elsevier Ltd. All rights reserved.