Theoretical studies on Lennard-Jones parameters of benzene and polycyclic aromatic hydrocarbons.

Lennard-Jones (L-J) parameters, collision diameter and well depth, of benzene and polycyclic aromatic hydrocarbons (PAHs) interacting with bath gases helium and nitrogen are studied theoretically in this work. The results of three different computing methods, called SA, -, - methods respectively, are compared with literature data. The SA method determines effective L-J parameters from the spherically averaged intermolecular potentials; the - method averages L-J parameters obtained from different relative orientations of interacting partners; and the - method uses an orientation-averaging rule on the basis of two characteristic variables and representing repulsive and attractive energy scales respectively.

On the determination of Lennard-Jones parameters for polyatomic molecules.

Characterizing the key length and energy scales of intermolecular interactions, Lennard-Jones parameters, , collision diameter and well depth, are prerequisites for predicting transport properties and rate constants of chemical species in dilute gases. Due to anisotropy in molecular structures, Lennard-Jones parameters of many polyatomic molecules are only empirically estimated or even undetermined. This study focuses on determining the effective Lennard-Jones parameters between a polyatomic molecule and a bath gas molecule from interatomic interactions.