Remark on the classical statistical mechanics of rigid molecules

Abstract

In principle the equation of state for rigid-body polyatomic molecules should depend upon the distribution of mass within the molecule as well as the intermolecular potential. It is shown, however, that no such dependence exists for molecules obeying the laws of classical mechanics, which implies that arbitrary axes within the molecules can be used in measuring relative positions and orientations in Monte Carlo simulations. The derivation involves the Jacobian of the transformation between sets of Euler angles and is used to show that equations used by Freasier et al. for hard dumb-bells are equivalent to those used by others.