Ab initio potential energy surface and intermolecular vibrational frequency of C₃-He complex

Abstract

The intermolecular potential energy surface for C₃–He complex has been constructed using supermolecular CCSD(T) and MP4 methods. The potential surfaces have been calculated for 27 values of R ranging from 2.8 to 8.0 Å and 19 values of θ equally spaced between 0° and 180°. Both CCSD(T) and MP4 potentials have similar global behaviors. The global minimum in each of the potentials corresponds to the slightly distorted T-shaped geometry. On the basis of these two potentials, the intermolecular vibrational energies and wavefunctions were calculated. The energy level pattern of the vdW vibrational states was predicted for C₃–He complex. The zero point bending motion of this complex has a range of 180°. The calculated fundamental frequency of vdW bending is 3.16 cm⁻¹ at CCSD(T) level, and 5.38 cm⁻¹ at the MP4 level. In addition, we have also constructed the intermolecular potential energy surface with C₃ bending coordinate of 160° by using supermolecular CCSD(T) method. Two local minima including arrow-shaped and Y-shaped configurations were determined. The rotational constants of three C₃–He structures including T-shaped, arrow-shaped and Y-shaped configurations at CCSD(T) level were also reported.

Keywords:

• C₃–He
• potential energy surface
• CCSD(T)
• vdW vibrational frequencies
• wavefunctions

Acknowledgements

The authors thank Professor Xie Daiqian of Nanjing University for providing his computer program and helpful discussions. This work was supported by National Natural Science Foundation of China (No. 20675049) and Natural Science Foundation of Shandong Province (No. Y2006B44).