Hard Disk PVT Measurement

This applet allows you to measure the pressure-volume-temperature (PVT) relationship for a system of hard disks. Observe the atom motions in one panel; notice that the particles interact with one another according to a pure hard repuslive potential. In the other panel observe averages for the pressure at different settings for the temperature and density. If you change the settings for the simulation (number of molecules and/or temperature), you can reset the simulation averages by pressing the corresponding button in the Averages panel.

The simulated system is surrounded by hard walls. Momentum transfer between the disks and the walls is used to measure the system pressure.

The simulation is conducted for a two-dimensional system. To permit the pressure and density to be reported in three-dimensional units (bar and mol/liter), the system is assumed to have a "depth" of 3.5 Angstroms. Note that this artificial term (which has no effect on the dynamics of the system) cancels upon taking the ratio PA/NkT. The disks are 2.8 Angstroms in diameter, and the simulation box is square with 35 Angstroms on each side.

Adjustment of the particle number halts the simulation. Press the "Continue" button to restart.