Synergistic effects of uniaxial strain and vacancy defect on the mechanical and magnetic properties of the C₃N monolayer

Using the first-principles calculations, we study the structural, mechanical, magnetic properties and electronic structures of the pristine and defective C3N monolayers with uniaxial tensile strains. Not only the C3N monolayer with a N vacancy (C3N-N) but also the C3N monolayer with a C vacancy (C3N-C) shows a strain-controlled local lattice deformation. The ultimate strain in the same direction is almost unaffected by missing atomic species. In particular, both C3N-N and C3N-C monolayers may embrace a more significant mechanical anisotropy compared to the pristine C3N monolayer, and show a dependence of mechanical anisotropy on uniaxial tensile strain. With increasing axial strain, the C3N-N monolayer retains metallicity, while the C3N-C monolayer displays a semiconductor-to-metal transition. The spin-polarized calculations indicate a vacancy-induced p-electron magnetism in both C3N-N and C3N-C monolayers, and the strain-tuning of p-electron magnetism is demonstrated. Therefore, manipulating the mechanical performance and magnetism of C3N monolayer through the synergy of vacancy defects and strains greatly broadens the application range of C3N monolayer materials.