Two-Dimensional C4N Global Minima: Unique Structural Topologies and Nanoelectronic Properties

Atomically thin 2D materials have drawn great attention due to their many potential applications. We herein report two novel structures of 2D C 4 N identified by first-principles calculations in combination with a swarm structure search. These two structures (with symmetry of Pm and P 2/ m ) are almost degenerate in energy (with only 4 meV/atom difference) and exhibit quite similar structural topologies, both consisting of alternative arrays of C–N hexagon and arrays of C–N pentagon–octagon–pentagon. The Pm structure is semiconducting with a direct band gap of 90 meV at HSE. In contrast, the P 2/m structure is a zero-band-gap semimetal and possesses the distorted Dirac cone, showing the direction-dependent Fermi velocity and electronic properties. Thus the predicted C 4 N monolayers are promising for applications in nanoelectronics.