A NEW POTENTIAL MODEL FOR CARBON-DIOXIDE FROM AB-INITIO CALCULATIONS

Ab initio quantum chemical calculations have been carried out for carbon dioxide dimer and the results have been used to establish potential functions usable in molecular simulations. Since the intermolecular interaction in carbon dioxide is fairly weak, careful treatment is required: this study uses 6-31G* basis set and takes electron correlations by the 2nd order Moller-Plesset theory into account. The potential energy surface is elucidated using the four representative relative configurations of the dimer. A new potential function model has been proposed on the basis of these ah initio data. In the super-critical region, this model is used to calculate the PVT relation of carbon dioxide fluid by the Monte Carlo simulations and confirmed to reproduce reasonably well the experimental isotherms.