Fluid interface tensions near critical end points

Abstract

Novel local free-energy functionals are presented, generalizing the de Gennes-Fisher critical-point ansatz, for obtaining fluid interface tensions near critical end points and critical wall tensions. Nonclassical exponents, proper analyticity in T, etc., are embodied. New ‘‘interpolated linear-model’’ and ‘‘trigonometric’’ parametric equations of state then lead to universal ratio estimates ${\mathit{K}}_{+}$/${\mathit{K}}_{\mathrm{-}}$≃-0.83, (${\mathit{K}}_{+}$+${\mathit{K}}_{\mathrm{-}}$)/K≃0.$1_2$, for the amplitudes K of the critical and ${\mathit{K}}_{\pm }$ of the noncritical wall tensions.