Adhesion and nonwetting-wetting transition in theAl/α−Al2O3

Using a reactive force field (ReaxFF), we investigated the structural, energetic, and adhesion properties, of both solid and liquid $\mathrm{Al}/\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ interfaces. The ReaxFF was developed solely with ab initio calculations on various phases of Al and ${\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ and Al-O-H clusters. Our computed lattice constants, elastic constants, surface energies, and calculated work of separation for the solid-solid interface agree well with earlier first-principles calculations and experiments. For the liquid-solid system, we also investigated the nonwetting-wetting transition of liquid Al on $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}(0001).$ Our results revealed that the evaporation of Al atoms and diffusion of O atoms in $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ lead to the wetting of liquid Al on the oxide surface. The driving force for this process is a decrease in interfacial energy. The nonwetting-wetting transition was found to lie in the 1000--1100 K range, which is in good agreement with sessile drop experiments.