Molecular dynamics simulations of fluid carbon dioxide using the model potential based on ab initio MO calculation

The nonbonding interaction energy of carbon dioxide dimer was calculated using several basis sets to evaluate the basis set effect. Large basis sets including diffuse polarized functions were necessary to evaluate the interaction energy correctly. Small basis sets considerably underestimate the interaction energy. Nonbonding parameters of a model potential of carbon dioxide were refined based on the interaction energies of 40 geometrical configuration dimers calculated by an MP2/6-311 + G(2df)-level ab initio method with the BSSE correction. The molar volume and heat of evaporation of liquid carbon dioxide obtained from molecular dynamics simulations with the model potential reproduced the experimental values with only a few percentage errors. On the other hand the model potential based on the BSSE uncorrected interaction energies overestimated the attractive interaction and failed to reproduce the experimental values. The same model potential also reproduced the experimental pressure and self-diffusion coefficient of super critical fluid satisfactorily.