REACTION VOLUMES IN MODEL FLUID SYSTEMS .2. DIATOMIC DISSOCIATION IN LENNARD-JONES SOLVENTS

A model diatomic dissociation reaction representing Br2 --> 2Br dissolved in rare gas solvents (Ne, Ar, and Xe) is examined using a Lennard-Jones perturbed hard sphere fluid theory. Properties of the appropriate bard sphere reference system are derived from the ''hard fluid'' two-cavity distribution function, and attractive solvation energies are calculated using Percus-Yevick reference-interaction-site model (PY-RISM) solvent distribution functions (about the bound and dissociated diatomic). Small changes (10-30%) in the solvent atom-solute atom attractive interaction well depth upon dissociation are found to qualitatively change the corresponding reaction free energies and volumes. Calculations are performed as a function of solvent temperature, density (pressure), and solute-solvent interaction parameters.