Effect of translational and angular momentum conservation on energy equipartition in microcanonical equilibrium in small clusters

Phys Rev E Stat Nonlin Soft Matter Phys. 2009 May;79(5 Pt 1):051101. doi: 10.1103/PhysRevE.79.051101. Epub 2009 May 1.

Abstract

We investigate numerically and analytically the effects of conservation of total translational and angular momentum on the distribution of kinetic energy among particles in microcanonical particle systems with small number of degrees of freedom, specifically microclusters. Molecular dynamics simulations of microclusters with constant total energy and momenta, using Lennard-Jones, Morse, and Coulomb plus Born-Mayer-type potentials, show that the distribution of kinetic energy among particles can be inhomogeneous and depend on particle mass and position even in thermal equilibrium. Statistical analysis using a microcanonical measure taking into account of the additional conserved quantities gives theoretical expressions for kinetic energy as a function of the mass and position of a particle with only O(1/N;{2}) deviation from the Maxwell-Boltzmann distribution. These expressions fit numerical results well. Finally, we propose an intuitive interpretation for the inhomogeneity of the kinetic energy distributions.

Publication types

  • Research Support, Non-U.S. Gov't