Fluid-Fluid Interfaces of Multi-Component Mixtures in Local Equilibrium

• Main Authors: Dick Bedeaux, Signe Kjelstrup
• Format: Article
• Language: English
• Published: MDPI AG 2018-04-01
• Series: Entropy
• Subjects: Gibbs interface; surface equation of state; dividing interface; local equilibrium; dynamic boundary conditions; phase transition
• Online Access: http://www.mdpi.com/1099-4300/20/4/250

We derive in a new way that the intensive properties of a fluid-fluid Gibbs interface are independent of the location of the dividing surface. When the system is out of global equilibrium, this finding is not trivial: In a one-component fluid, it can be used to obtain the interface temperature from the surface tension. In other words, the surface equation of state can serve as a thermometer for the liquid-vapor interface in a one-component fluid. In a multi-component fluid, one needs the surface tension and the relative adsorptions to obtain the interface temperature and chemical potentials. A consistent set of thermodynamic properties of multi-component surfaces are presented. They can be used to construct fluid-fluid boundary conditions during transport. These boundary conditions have a bearing on all thermodynamic modeling on transport related to phase transitions.