Strong mechanical anisotropy and an anisotropic Dirac state in 2D C 5 N 3 .

Two-dimensional (2D) carbon nitride materials have emerged as a versatile platform for the design of high-performance nanoelectronics, but strong anisotropy in 2D carbon nitrides has rarely been reported. In this work, a 2D carbon nitride with strong anisotropy composed of tetra-, penta-, and hexa-rings (named as TPH-C 5 N 3 ) is proposed. This TPH-C 5 N 3 exhibits both dynamical and mechanical stability. Furthermore, it also showcases remarkable thermal stability, reaching up to 2300 K, as evidenced by AIMD simulations conducted in an NVT environment utilizing the Nosé-Hoover thermostat. Significantly, TPH-C 5 N 3 demonstrates high anisotropic ratios in its mechanical properties, positioning it as the frontrunner in the current carbon nitride systems. In addition, a Dirac cone with an anisotropic ratio of 55.8% and Fermi velocity of 7.26 × 10 5 m s -1 is revealed in TPH-C 5 N 3 . The nontrivial topological properties of TPH-C 5 N 3 are demonstrated by a non-zero Z 2 invariant and topologically protected edge states. Our study offers theoretical insights into an anisotropic 2D carbon nitride material, laying the groundwork for its design and synthesis.