where i is the interfacial system of interest (sl, sv, or lv), j correspond to the references (sv, lv, s, or l), and n j is the number of atoms or molecules in the corresponding system. Thus, the chemical potentials are considered as free energies per component j by µ j = F j (n)/n. In case the reference state itself contains an interface of area A i , the free energy can be endowed with a surface work term such that the chemical potential assumes the form µ j = (F bulk j (n) + γ j A i )/n. The adsorption energy of a single water molecule can be obtained by reducing Eq. ( ) to