Unveiling Vacancy-Driven Stability: Atomic and Electronic Insights into Ni/Al₂O₃ Interfaces

The Ni/Al₂O₃ interface bears the load transfer and energy dissipation, which determines the service performance of the composite materials. In this study, three distinct vacancy-defect-modified interface models (D₁, D₂, and D₃, corresponding to vacancies in the first, second, and third layers of the Ni substrate surface, respectively) were constructed to systematically investigate the regulatory mechanism of vacancies on interfacial stability. The underlying mechanism of vacancy-enhanced interfacial stability was elucidated from both atomic-scale structural and electronic property perspectives. The results demonstrate that the D₁, D₂, and D₃ structures increase the adhesion work of the interface by 2.0%, 6.7%, and 0.3%, respectively. This enhancement effect mainly stems from vacancy-induced atomic relaxation at the interface, which optimizes the equilibrium interfacial spacing and effectively releases residual strain energy. Further electronic structure analysis reveals a notable increase in charge density at the vacancy-modified interface (particularly in the D₂ structure), indicating that vacancy defects promote charge transfer and redistribution by altering local electron distribution. More importantly, the bonding strength of the interface exhibits a positive correlation with electron orbital hybridization intensity, where stronger s-, p-, and d-orbit hybridization directly leads to a more stable interface. These findings provide atomic- and electronic-scale insights into the mechanistic role of vacancy defects in governing bonding at the Ni/Al₂O₃ interface.