Ab initio calculation of the potential energy surface for the large-amplitude bending and symmetric stretching vibration in the electronic ground state of XeF2

A two-dimensional symmetric stretching-bending potential surface for the electronic ground state of the XeF₂ molecule has been computed by means of self-consistent field and multi-reference configuration interaction methods. At the correlated level of treatment it is found that the linear nuclear arrangement of XeF₂ with XeF bond distances close to 200 pm corresponds only to a local minimum on the potential energy surface separated from the dissociation products Xe + 2F by a high energy barrier. The results of a vibrational analysis study enable a reliable reproduction and interpretation of available experimental data concerning the infrared spectrum of the molecule.