First-Principles Investigation of the Electronic and Mechanical Properties of Graphitic Nitrogen Doping in Graphene: A Minimal Concentration Approach Using a √7 × √7 × 1 Supercell
摘要
Graphene’s exceptional properties make it a prime platform for advanced materials research, yet its intrinsic zero-bandgap limits its nanoelectronic applications. Here, first-principles density functional theory (DFT) calculations are used to assess how graphitic (substitutional) nitrogen modifies the structural, electronic, and mechanical responses of graphene. A hexagonal √7 × √7 × 1 supercell (14 atoms) with a single N atom (7.14 at.%) is adopted to capture localized dopant effects while preserving lattice symmetry. The doped configuration is confirmed to be stable both thermodynamically (formation energy = 0.61 eV) and dynamically, as evidenced by phonon dispersions free of imaginary frequencies. Nitrogen incorporation causes a slight bond-length contraction and an upward shift of the Fermi level (≈ 0.68 eV), accompanied by the opening of a small band gap (≈ 0.20 eV), indicative of n-type behavior. Mechanically, the in-plane stiffness increases from 338.86 N/m to 409.89 N/m, attributable to strengthened N–C bonding, while the ultimate tensile strength and fracture strain show modest reductions. Overall, low-concentration graphitic N doping provides an effective route to simultaneously tune band structure and stiffness in graphene, offering guidance for the design of nanoelectronic, sensing, and flexible-device architectures.