Also contains definitions of: differential molar interfacial energy, differential molar surface excess energy
https://doi.org/10.1351/goldbook.D01705
When the addition of a differential amount or is effected at constant gas volume, the differential molar energy of adsorption of component , or , is defined as: or where the differential molar surface excess energy, , is given by and the differential molar interfacial energy, , by is the differential molar energy of component in the gas phase, i.e.