A new 2D auxetic CN2 nanostructure with high energy density and mechanical strength

TL;DR

This paper predicts a new 2D CN2 nanostructure with high energy density, exceptional mechanical properties, and tunable electronic band gap, promising for energy storage, nanomechanics, and electronic applications.

Contribution

It introduces a novel 2D CN2 structure with confirmed stability, high energy density, and unique mechanical and electronic properties, expanding the potential of 2D materials.

Findings

High energy density of 6.3 kJ/g.

Negative Poisson's ratio and high stiffness.

Tunable band gap from 3.37 to 4.57 eV.

Abstract

The existence of a new two dimensional CN2 structure was predicted using ab-initio molecular dynamics (AIMD) and density-functional theory calculations. It consists tetragonal and hexagonal rings with C-N and N-N bonds arranged in a buckling plane, isostructural to tetrahex-carbon allotrope. It is thermodynamically and kinetically stable suggested by its phonon spectrum and AIMD. This nanosheet has high concentration of N and contains N-N single bonds with an energy density of 6.3 kJ/g, indicating potential applications as high energy density materials. It possesses exotic mechanical properties with negative Poisson's ratio and an anisotropic Young's modulus. The modulus in the zigzag direction is predicted to be 340 N/m, stiffer than h-BN and penta-CN2 sheets and comparable to graphene. Its ideal strength of 28.8 N/m outperforms that of penta-graphene. The material maintains phonon stability upon the application of uniaxial strain up to 10% (13%) in the zigzag (armchair) direction or biaxial strain up to 5%. It possesses a wide indirect HSE band gap of 4.57 eV which is tunable between 3.37 - 4.57 eV through strain. Double-layer structures are also explored. Such unique properties may have potential applications in high energy density materials, nanomechanics and electronics.