Dynamics of vibrated granular monolayers

We study statistical properties of vibrated granular monolayers using molec ular dynamics simulations. We show that at high excitation strengths, the s ystem is in a gas state, particle motion is isotropic, and the velocity dis tributions are Gaussian. As the vibration strength is lowered, the system's dimensionality is effectively reduced from three to two. Below a critical excitation strength, a cluster phase occurs, and the velocity distribution becomes bimodal. In this phase, the system consists of clusters of immobile particles arranged in close-packed hexagonal arrays, and gas particles who se energy equals the first excited state of an isolated particle on a vibra ted plate.