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MEDEA GIBBS: Liquid - Vapor Pressure Curve of Methane

MEDEA GIBBS calculates equilibrium properties of fluids either pure or mixed, in a single phase or in multiple phases, using a force field based Gibbs ensemble technique.
The present application note focuses on the vapor pressure curve of methane, in other words we will deal with a one-component two-phase system.

In modeling this system we are limited to a rather small number of particles, typically a few
hundred to keep computational efforts within limits. In MEDEA GIBBS we therefore define
two boxes containing the liquid and the gas phase respectively. Technically this means that
we squeeze many more particles into a volume unit for the liquid phase than we do for the
gas phase resulting in a higher starting density of articles in the box representing the
liquid.

During the computation, we allow for random moves of the rotations and moves between the boxes.
For each move into a new configuration a “penalty” function is calculated using force fields and over the duration of the simulation a minimum energy configuration is established.

In this final or equilibrium configuration, particles are distributed over both the liquid and the gas phase, provided that the initial temperature lies in the range of liquid-vapor coexistence.

Full Version (pdf): 
application/pdf iconMedeA Gibbs %97 Liquid - Vapor Pressure Curve of Methane.pdf