Multiscale cascade triggered by the vacancy-[Si + C] synergy in β-SiC: a first-principles study of electron-structure-dynamics coupling

molecular dynamics (AIMD) to systematically investigate the vacancy-[Si + C] in β-SiC to reveal its function as a cooperative defect unit that triggers multiscale instability. Unlike a linear superposition of individual vacancy effects, the vacancy-[Si + C] induces nonlinear synergy and initiates with electron cloud delocalization evidenced by fragmented electron localization function. This electronic perturbation cascades into severe short-range lattice disorder, suppressed mid-range atomic mobility and global phonon mode softening. We elucidate a coherent electron-structure-dynamics coupling mechanism. Vacancy-[Si + C] as a synergistic defect core whose coupled lattice strain and electron delocalization effect destroy the periodic bonding of β-SiC, causing large-scale lattice disorder. This work establishes a novel defect-origin perspective for irradiation damage in β-SiC, revealing the vacancy-[Si + C] as a prototypical synergistic defect seed that triggers a multiscale damage cascade. The coupled electron-structure-dynamics approach developed here offers a generalizable paradigm for deciphering complex defect behaviors in covalent materials, providing critical guidance for vacancy-engineering strategies in β-SiC based functional materials.