A Method to Calculate the g-Coefficients of the Molecular Pair Correlation Function from Molecular Dynamics Simulations

Abstract

It is known that the rotational equation of motion of rigid molecules in MD simulations can be solved in a singularity-free form if quaternions are used for the description of the rotational motion. We show that these quaternions are also suited for the calculation of the so-called ‘g-coefficients’, which are the expansion coefficients of the molecular pair correlation function (MPCF) in terms of Wigner functions. This is due to the fact that quaternions arc themselves a representation of the rotation group and can be referred to an arbitrary coordinate frame in a particularly simple way. As an application for the quaternion formalism we calculate some g-coefficients of the MPCF of methylene chloride (CH2 Cl2 ).