We model the solid/liquid interface by a (non-symmetric) three-layer 3 × 4 Au(111) slab with the two bottom layers kept fixed and roughly three layers of interfacial water (24 H 2 O molecules) on top. Periodic boundary conditions are applied in all three directions. We separate the systems by about 14 Å of vacuum in the z-direction perpendicular to the surface and include dipole corrections. The energy levels that enter Fig. at an (absolute) potential U close to 0 V vs. the standard hydrogen potential (SHE). 17