where ⟨v α (0)v α (t)⟩ is the VACF of species α, and ω is the frequency. The VDOS for the fluid, D P AO4 (ω), was calculated for all fluid atoms falling within the first adsorption layer and the VDOS for the surface, D Fe 2 O 3 (ω), was calculated for all surface atoms within a 5 Å distance from interface. After sampling various correlation times for the VACF, we determined that a correlation time of 4 ps provided the optimal balance, yielding comprehensive vibrational information while minimizing noise in the resulting VDOS. During this time, < 5% of initial interfacial PAO4 molecules had left the region. The same systems as used for the ITR calculations were also used for the VDOS calculations.