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The '''test area method''' is related to the [[test volume method]] for the calculation of the [[pressure]] (which, in turn, is related to [[Widom test-particle method]]). The [[surface tension]] of a planar [[interface]] is given by the change in [[internal energy]] <math>\Delta U</math> caused by "squeezing" the system: modifying both the length in the direction normal to the interface and the area in the plane of the interface, in such a way that the total volume is left unchanged. | The '''test area method''' is related to the [[test volume method]] for the calculation of the [[pressure]] (which, in turn, is related to [[Widom test-particle method]]). The [[surface tension]] of a planar [[interface]] is given by the change in [[internal energy]] <math>\Delta U</math> caused by "squeezing" the system: modifying both the length in the direction normal to the interface and the area in the plane of the interface, in such a way that the total volume is left unchanged. | ||
It can be shown that the surface tension, if the changes are small, is given by | It can be shown that the surface tension, if the changes are small, is given by: | ||
< | :<math> \gamma = - \frac{ k_B T \Delta A } \log\langle \exp(-\Delta U/k_B T)\rangle. </math> | ||
: | The expression parallels the one for the pressure in the [[test volume method]]; the advantages of this technique are also similar: avoidance of force calculation, easiness for discontinuous potential... | ||
==References== | ==References== | ||
#[http://dx.doi.org/10.1063/1.2038827 Guy J. Gloor, George Jackson, Felipe J. Blas and Enrique de Miguel "Test-area simulation method for the direct determination of the interfacial tension of systems with continuous or discontinuous potentials", Journal of Chemical Physics '''123''' 134703 (2005)] | |||
[[category: computer simulation techniques]] | [[category: computer simulation techniques]] |