surface excess Gibbs energy

Defined by

$G σ = H σ − T S σ = A σ − γ A s$

where $H σ$ is the surface excess enthalpy, $T$ is the thermodynamic temperature, $S σ$ is the surface excess entropy, $A σ$ is the surface excess Helmholtz energy, $γ$ is the surface tension, and $A s$ is the area relative to a Gibbs surface.

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