Multiscale investigation of single-vacancy defects in 2D C₆₀ crystals

The recent synthesis of two-dimensional C₆₀ crystals (2D C₆₀) has unveiled a new class of carbon semiconductors with tunable bandgaps and exceptional thermal stability. While the perfect properties of 2D C₆₀ have been extensively characterized, the impact of intrinsic defects, which is inevitable in practical applications, remains largely unexplored. In this study, we systematically investigated the stability, magnetism, electronic, and mechanic properties of all 16 single-vacancy defects in 2D C₆₀ using first-principles calculations, followed by a multiscale analysis of their mechanical response via a machine learning neuroevolution potential (NEP). Our study reveals multiple physical effects induced by single-vacancy defects in 2D C₆₀. We found that the lattice reconstruction stabilizes the defect thermodynamically but leads to bandgap closure and metallization. Rich magnetic properties including non-magnetic, ferromagnetic and anti-ferromagnetic states can be induced by the vacancy defects. We also found pronounced anisotropy and a generally degradation of ideal strength, with no direct correlation observed between thermodynamic stability and mechanical integrity. Furthermore, using large-scale molecular dynamics simulations, we found a critical temperature-dependent failure mechanism. This work provides theoretical support for defect engineering in 2D C₆₀ and paves the way for its practical applications.