Binding Energetics of Dimethyl Ether and Sulfur Dioxide Using Both Ab Initio and Molecular Simulation Methods

Both molecular simulation and ab initio methods were utilized to determine the binding energies between pairs of dimethyl ether (DME) and sulfur dioxide (SO2) molecules. Three molecular orientations for each combination of molecules (DME-DME, DME-SO2 and SO2-SO2) were examined at the Hartee-Fock (HF), B3LYP and Moller-Plesset 2 (MP2) levels of theory. Basis sets ranging from 3-21g up to 6-311g+(d,p) were used. Both the ab initio and predictions of classical force fields, revealed that the unlike molecule interactions were stronger than the like molecule interactions. Such relative interactions are necessary for the formation of minimum pressure azeotropy. To further investigate atomic level interactions in these systems, a Kitaura-Morokuma analysis was performed using GAMESS. Finally, vapor-liquid equilibria for pure DME and SO2 is shown to obtain the minimum pressure azeotrope but with an azeotope depth not in good agreement with experimental data at a temperature of 363K. Investigations into the interactions between this system and two other systems, with different models of sulfur dioxide, are presented.