Basis set effects on the intermolecular interaction of the CF₄-CF₄ system

The intermolecular potential energy surface of the CF₄-CF₄ system is explored by means of ab initio molecular orbital calculations at the HF and MP2 level of theory. A number of progressively larger basis sets (up to 6- 311+G(3d)) are used in order to evaluate the basis set effect. The HF energy component of the total interaction energy is somewhat affected by the choice of the basis set. The second-order correlation correction E(2) to the interaction energy is greatly changed with the choice of the basis set. The nonbonding parameters of the Lennard-Jones and the Buckingham potential energy functions are fitted to the ab initio MP2/6-31+G(3d) interaction energies for nine different orientations and a total of 130 configurations. (C) 2000 Elsevier Science B.V.