Particle Dynamics

The hard sphere fluid (or hard disk in 2 dimensions) provides a very simple model of a fluid. Imagine a large box, almost filled with ball bearings, and suspended in zero gravity. (Gravity is irrelevant on a microscopic scale.) Many features of real fluids are captured by this model, such as the fluid-solid phase transition.

In this simulations, the disks are moved using a Monte Carlo dynamics. A trial move is generated by displacing a single particle by a random amount. This move is accepted as a new configuration only if the particle does not overlap with any other particle. Else the old configuration is retained.

The Lennard-Jones fluid is realistic model of a simple associative fluid, such as Argon. The particle-particles interaction contains a very strong, short ranged repulsion, and a medium ranged attraction. Particles like to be close, but not too close.

In this simulation the particles are moved using molecular dynamics. The trajectory is found by integrating Newton's equations of motion. This provides both dynamical and structural information.