surface excess energy

https://doi.org/10.1351/goldbook.S06173
Defined by: \[U^{\unicode[Times]{x3C3} } = U - U^{\unicode[Times]{x3B1} }- U^{\unicode[Times]{x3B2} }= U - V^{\unicode[Times]{x3B1} }\ \frac{U_{\text{m}}^{\unicode[Times]{x3B1} }}{V_{\text{m}}^{\unicode[Times]{x3B1} }} - V^{\unicode[Times]{x3B2} }\ \frac{U_{\text{m}}^{\unicode[Times]{x3B2} }}{V_{\text{m}}^{\unicode[Times]{x3B2} }}\] where \(V^{\unicode[Times]{x3B1} }\) and \(V^{\unicode[Times]{x3B2} }\) satisfy the condition \(V^{\unicode[Times]{x3B1} } + V^{\unicode[Times]{x3B2} } = V\), the total volume of the system. (\(\frac{U_{\text{m}}^{\unicode[Times]{x3B1} }}{V_{\text{m}}^{\unicode[Times]{x3B1} }}\)) and (\(\frac{U_{\text{m}}^{\unicode[Times]{x3B2} }}{V_{\text{m}}^{\unicode[Times]{x3B2} }}\)) are the energy densities in the two bulk phases where \(U_{\text{m}}^{\unicode[Times]{x3B1} }\) and \(U_{\text{m}}^{\unicode[Times]{x3B2} }\) are the mean molar energies and \(V_{\text{m}}^{\unicode[Times]{x3B1} }\) and \(V_{\text{m}}^{\unicode[Times]{x3B2} }\) are the mean molar volumes of the two phases.
Source:
PAC, 1972, 31, 577. (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 599 [Terms] [Paper]