Ab initio calculation of the intermolecular potential energy surface of (CO2)2 and first applications in simulations of fluid CO2 Original Research Article

A four-dimensional potential energy surface for the carbon dioxide dimer composed from rigid monomers is determined. 226 energy points were calculated ab initio with a large basis set on the MP2 level including full counterpoise correction. An analytical site-site potential is fitted to these points. The stationary points of the analytical surface are determined, harmonic vibrational frequencies and second virial coefficients are calculated and compared to experimental values. The potential energy surface is applied in molecular dynamics simulations to obtain pair distribution functions of supercritical and liquid carbon dioxide, which are compared to experiment. In addition some state points of the phase diagram are calculated.