AB-INITIO CALCULATION OF THE INTERMOLECULAR POTENTIAL-ENERGY SURFACE OF (CO2)(2) AND FIRST APPLICATIONS IN SIMULATIONS OF FLUID CO2

A four-dimensional potential energy surface for the carbon dioxide dim er 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 fi tted to these points. The stationary points of the analytical surface are determined, harmonic vibrational frequencies and second virial coe fficients are calculated and compared to experimental values. The pote ntial energy surface is applied in molecular dynamics simulations to o btain pair distribution functions of supercritical and liquid carbon d ioxide, which are compared to experiment. In addition some state point s of the phase diagram are calculated.