Continuum-Model Treatment of Long-Range Intermolecular Forces. I. Pure Substances

A theory is presented whereby the long-range intermolecular forces, including the London dispersion forces, of pure nonelectrolytes may be calculated from optical and dielectric data. The method is based on the continuum-model approach, where one molecule is treated explicitly while the others are replaced by a medium of uniform dielectric. The classical and quantum-mechanical oscillators are used as working models and expressions are derived for computing the cohesive energy appropriate for both types of oscillators. The potential energy based on the quantum-mechanical oscillator is calculated for a number of liquids and is shown to be in fair agreement with the experimental energy of vaporization.