In more recent AIMD simulations, a more detailed picture of interfacial water molecules has emerged. At the Pt(111)-water interface, a fraction of water molecules are bound strongly through their oxygen atom with the metal so that the hydrogen atoms of the water molecule are above the oxygen atom. This is called the O-down configuration, corresponding to α w = 0° in this model. A bit further away from the metal surface are resided another type of water molecules which can be further divided into the H-down (α w = 180°) and H-up (α w = 0°) configurations. The AIMD results suggest 𝛿𝜇 ̃< 0 in the present model.