Ab initio potential energy surface and intermolecular vibrational frequencies of C3-Ar complex

The intermolecular potential energy surfaces for C-3-Ar have been calculated by supermolecular CCSD(T) and MP4 methods. The MP4 and CCSD(T) potentials have similar global behaviours. Their global minima all correspond to the slightly distorted T-shaped geometries. From these two potentials, the intermolecular vibrational energies and wavefunctions were calculated. The energy level patterns of the vdW vibrational states were predicted for the C-3-Ar complex. The zero point bending motion of this complex has a range of approximately 60 degrees. The calculated transition frequencies of vdW bending agree well with available experimental data.