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The Lennard-Jones PVT System simulates a 2D system of particles confined between a thermal reservoir and a piston. This computer model is designed to study the equation of state for particles interacting via a simple but realistic molecular potential that has a weak long-range attraction and a strong short range repulsion. Slow-moving particles are color-coded as blue and fast particles are color-coded as yellow. Users can set the initial particle energy, the initial particle separation, and the thermal reservoir temperature Tr. The thermal conductivity parameter ? determines the probability that a collision with the thermal wall will affect (thermalize) the colliding particle. If the conductivity is one, the particle velocity after a reservoir collision is set according to Maxwell-Boltzmann statistics. If the conductivity is zero, all reservoir collisions are elastic and the total internal energy E of the system is conserved.
The piston input fields in the bottom panel are used to compress and expand the system. Users can approximate an adiabatic compression by setting ?=0 and can approximate an isothermal compression by setting ?=1. The piston speed must, of course, be small to insure that the system remains in equilibrium during the compression for a (quasi-static approximation) reversible process. Separate windows allow users to follow the change in state of the system on a PV plot or a time evolution plot.
The Lennard-Jones PVT model is a supplemental simulation for the article "Pressure Oscillations in Adiabatic Compression" by Roland Stout in The Physics Teacher 49(5), 280-281 (2011) and has been approved by the author and The Physics Teacher editor. The model was developed using the Easy Java Simulations (Ejs) modeling tool and is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_stp_md_LennardJonesPVTSystem.jar file will run the program if Java is installed.
Last Modified July 14, 2013
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The source code zip archive contains an EJS-XML representation of the Lennard-Jones PVT System. Unzip this archive in your EJS workspace to compile and run this model using EJS.
Last Modified March 12, 2011