Computation of phase equilibria: Difference between revisions
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The computation of phase equilibria using computer simulation can follow different strategies. | The computation of phase equilibria using computer simulation can follow different strategies. | ||
== Liquid-vapor equilibria of one component systems == | == Liquid-vapor equilibria of one component systems == | ||
The thermodynamic equilibrium implies, for two phases <math> \alpha </math> and <math> \beta </math>: | The thermodynamic equilibrium implies, for two phases <math> \alpha </math> and <math> \beta </math>: | ||
* Equal temperature: <math> T_{\alpha} = T_{\beta} </math> | |||
* Equal pressure: <math> p_{\alpha} = p_{\beta} </math> | |||
* Equal chemical potential: <math> \mu_{\alpha} = \mu_{\beta} </math> | |||
=== Independent simulations for each phase at fixed <math> T </math> in the [[canonical ensemble]] === | |||
The simulations can be carried out either using [[Monte Carlo]] or [[Molecular dynamics]] techhniques. | |||
Let us assume that we have some knowledge on the phase diagram of the system. We could: | |||
- Fix a temperature | |||
- Perform a few simulations in the low density region (where the gas phase density is expected to be) | |||
- Perform a few simulations in the moderate / high density regions (where the liquid phase should appear) | |||
- In these simulations we can compute for each density (at fixed T) the values of the pressure and the | |||
chemical potentials (for instance using the [[Widom test-particle method]]) | |||
Revision as of 17:46, 21 September 2007
[CURRENTLY WORKING ON THE PAGE]
The computation of phase equilibria using computer simulation can follow different strategies.
Liquid-vapor equilibria of one component systems
The thermodynamic equilibrium implies, for two phases and :
- Equal temperature:
- Equal pressure:
- Equal chemical potential:
Independent simulations for each phase at fixed in the canonical ensemble
The simulations can be carried out either using Monte Carlo or Molecular dynamics techhniques. Let us assume that we have some knowledge on the phase diagram of the system. We could:
- Fix a temperature
- Perform a few simulations in the low density region (where the gas phase density is expected to be)
- Perform a few simulations in the moderate / high density regions (where the liquid phase should appear)
- In these simulations we can compute for each density (at fixed T) the values of the pressure and the chemical potentials (for instance using the Widom test-particle method)