Surface tension

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The surface tension, , is a measure of the work required to create a surface.

Thermodynamics

In the Canonical ensemble the surface tension is formally given as:

;

where

  • is the number of particles
  • is the volume
  • is the temperature
  • is the surface area
  • is the Helmholtz energy function

Computer Simulation

A review on different techniques to compute surface (interface) tension can be found in the paper by Gloor et al.

Liquid-Vapour Interfaces of one component systems

Binder procedure

For given conditions of volume and temperature, the Helmholtz energy function is computed as a function of the number of molecules:

The calculation is usually carried out using Monte Carlo simulation

If liquid-vapour equilibrium occurs, the plot of the chemical potential, , as a function of shows a loop.

Using basic thermodynamic procedures (Maxwell construction) it is possible to compute the densities of the two phases;

Explicit interfaces

Mixtures

References

  1. K. Binder "Monte Carlo calculation of the surface tension for two- and three-dimensional lattice-gas models", Physical Review A 25 pp. 1699 - 1709 (1982)

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