where 𝛼 𝑖 is the angle between the 𝑖 th water and the local electric field 𝐸 loc , 𝛿𝜇 is the chemical potential difference between the case of 𝛼 w = 0° and the case of 𝛼 w = 180°. The introduction of 𝛿𝜇 accounting for chemical interactions between water molecules and the metal surface is, to the best of my knowledge, a novel modification to the Watts-Tobin model.