## 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]