Influence of multipolar and induction interactions on the speed of sound

At large distances between molecules, the intermolecular forces are essenti ally attractive. They can be classified conveniently into three types, that is, multipolar, induction, and dispersion forces. We consider rigid nonlin ear molecules with enough symmetry so those principal axes of the quadrupol e tensor of the polarizibility coincide. Multipolar and induction interacti ons are calculated with the help of quantum mechanical calculations of the intermolecular energy function and the help of perturbation theory. The mul tipole expansion is terminated at the quadrupole term. The focus is on the development of a mathematical model fur calculation of the influence of mul tipole and induction interactions on the speed of sound and other thermodyn amic functions of state. For the calculation of the thermodynamic functions of state, perturbation theory with the Lennard-Jones potential as the refe rence is used. The thermodynamic and structural properties of the Lennard-J ones system are known from Monte Carlo and molecular dynamics computer simu lations. All important contributions are featured (translation, rotation, i nternal rotation, vibration, intermolecular potential energy, and the influ ence of electron and nuclei excitation). The analytical results are compare d with the experimental data and models obtained by classical thermodynamic s and show relatively good agreement.