Si ₃ N ₄ Monolayer with Interlocked Lieb Lattices: Wide-Bandgap Semiconductor with Dirac Features, Auxetic Mechanical Response, and Li Storage Capability

High Resolution Image Download MS PowerPoint Slide Nitride-based two-dimensional (2D) materials have attracted considerable interest due to their structural versatility and tunable electronic properties. In particular, lattice geometries capable of hosting flat bands and Dirac-like dispersions provide opportunities for engineering unconventional electronic states. Here, using first-principles calculations combined with particle swarm optimization, we predict a Si 3 N 4 monolayer composed of two interlocked Lieb sublattices forming an A 2 MX 4 -type structure. Phonon dispersion analysis and finite-temperature ab initio molecular dynamics simulations confirm its dynamical and thermal stability. Electronic structure calculations reveal that the Si 3 N 4 monolayer is a wide-bandgap semiconductor with an indirect bandgap. In addition to a spin-1 Dirac cone characteristic of Lieb-type lattices, the system exhibits a Dirac-like band crossing whose degeneracy is lifted by spin–orbit coupling. Distinct AA- and AB-stacked bilayer configurations are identified, with AA stacking exhibiting stronger interlayer coupling. Li adsorption and diffusion analyses indicate favorable binding at the square-vacancy sites and kinetically accessible penetration and migration pathways. These findings highlight the potential of lattice-engineered Si 3 N 4 as a stable 2D semiconductor platform with tunable interlayer interactions and Li storage capability.