Supplementary Information

Dimensions of the simulation boxes. Al coordination numbers of AlFx formed on alumina/aluminum metal heterostructures. Reaction kinetics for HF dissociation and Arrhenius plots for calculating the HF dissociation barriers. Figures illustrating HF dissociation events and conversion rection mechanisms. Numerical evolutions of -OH vs -F and -H vs -F in alumina and heterostructures, respectively. Snapshots showing primary products during the reactions. Mean squared displacement curves of Al atoms from the metal layer with their corresponding linear fits used to calculate the effective diffusion coefficient. Evidence showing that pre-melting of the aluminum metal layer in the alumina/aluminum heterostructure likely results from nanoscale effects rather than an underestimation of Al-Al interactions in the force field. Force field parameters of the Al/O/H/F force field.