Molecular dynamics study of the adhesion of Cu/SiO₂ interfaces using a variable-charge interatomic potential

The structural, adhesive, and electronic properties of Cu/α- cristobalite SiO₂ interfaces with various interface terminations are investigated with molecular dynamics simulations using the charge-optimized many-body (COMB) potential. We predict that the Cu/α-cristobalite interface exhibits the largest adhesion energy for the oxygen-richest condition. The trend of the adhesion energies is consistent with that determined from density functional theory (DFT) calculations. We also investigate the properties of Cu/α-quartz SiO₂ interfaces with different terminations, and show that the trend of adhesion energies is analogous to that of Cu/α-cristobalite interfaces. The adhesion energies of Cu/amorphous SiO₂ interfaces with different oxygen defect densities are also investigated, and the predicted adhesion energies are compared to experimental values. In particular, it is found that the adhesion energies decrease as the number of oxygen vacancies increases. The calculated charge differences across the interfaces with COMB are also consistent with the DFT electron-density difference analysis. These results demonstrate the ability of the empirical, variable-charge COMB potential to capture the key physical aspects of heterogeneous interfaces, including predicting that the adhesion of Cu/SiO ₂ interfaces increases with interfacial oxygen densities.