Two-Dimensional B ₄ C ₄ N ₂ Monolayer: A First-Principles Study of Directional-Dependence Mechanical and Electronic Properties

Two-dimensional (2D) materials are crucial for next-generation electronics, yet the design of light-elemental 2D materials and their stability and strain-responsive properties remain underexplored. Here, we propose a novel light-elemental 2D material through first-principles calculations─an atomically thin B4C4N2 monolayer with exceptional stability and strain-tunable electronic properties. It is revealed that B4C4N2 monolayer exhibits metallic characteristics featuring Dirac-like electronic states near the Fermi level and has remarkable mechanical robustness, with a Young’s modulus of ∼24 GPa under biaxial compressive strain and ∼7.5 GPa under biaxial tensile strain, coupled with distinct anisotropy. Notably, the system undergoes significant strain-induced phase transitions: a metal-to-semiconductor transition emerges at 10% biaxial tensile strain, while a nonmagnetic-to-magnetic transition occurs within the 20.5%–35% uniaxial (x-axis) strain range. These findings not only unveil a new member in the family of light-element 2D materials but also highlight its promising applications for developing flexible nanoelectronics and strain-engineered spintronic devices.