Dimensional model for the calculation of thermodynamic properties of gaseous molecules and ions

A dimensional analysis of the classical partition function for ionic molecules leads to simple universal relations for the calculation of nonelectronic entropies and free energy functions. The model is tested for a large number of species with different stoichiometries and degrees of ionicity (MX, MX2, M2X2, and ions MX/sup plus-or-minus1/). The success of these tests demonstrates the validity and usefulness of the model. Since the only quantities required for the calculation are the interatomic distance and atomic masses, this procedure can greatly simplify the calculation of these thermodynamic functions for an unknown species. As an illustration, calculated thermodynamic data are presented for the seven alkali halide dimers for which data are not available