Abstract: Two-dimensional (2D) Si_xC_y materials have become a research hotspot in materials science due to their unique structural tunability and outstanding physicochemical properties. Among these, 2D Si₂C₆, Si₆C₁₂ and Si₁₂C₂₀ are theoretically predicted to represent a novel class of topological insulator materials. Si₂C₆ and Si₁₂C₂₀ are semimetallic materials exhibiting Dirac cones, while Si₆C₁₂ is a high-order topological insulator with an intrinsic large bandgap. Currently, the regulation of electronic properties in two-dimensional Si_xC_y (Si₂C₆, Si₆C₁₂ and Si₁₂C₂₀) materials by stress remains to be investigated. In this study, first-principles density functional theory (DFT) was employed to investigate the strain-induced electronic properties of 2D Si_xC_y (Si₂C₆, Si₆C₁₂ and Si₁₂C₂₀) materials. Computational results reveal that near the biaxial tensile fracture strain, the Dirac cones of Si₂C₆ and Si₁₂C₂₀ remain intact. However, even small biaxial compressive strains or uniaxial strains disrupt the degeneracy at the Dirac points of Si₂C₆ and Si₁₂C₂₀, transforming them from topological insulators into trivial direct-bandgap semiconductors. Furthermore, biaxial strain modulates bandgap of the higher-order topological insulator Si₆C₁₂. Under 0-4% compressive strain, the bandgap decreases with increasing compressive strain. Under 0-10% tensile strain, the bandgap increases with increasing biaxial tensile strain. The bandgap of Si₆C₁₂ exhibits significant sensitivity to strain variations, making it a promising candidate for semiconductor devices. Near fracture strain, the valence and conduction bands of Si₆C₁₂ intersect, resulting in metallic behavior. Under uniaxial strain, tensile or compressive deformation induces band delocalization at the Γ point. Additionally, classical molecular dynamics (MD) simulations were employed to investigate the mechanical properties of Si₂C₆, Si₆C₁₂, and Si₁₂C₂₀. Results indicate that the fracture strengths of these materials decrease as the C/Si ratio reduces. The fracture strains of Si₂C₆, Si₆C₁₂, and Si₁₂C₂₀ range from 0.32 to 0.37, exceeding those of single-crystal graphene and defect-free hexagonal boron nitride, and demonstrating excellent ductility.

Key words: first-principles calculation, two-dimensional Si_xC_y material, strain regulation, electronic property, mechanical property