CH4·F− revisited: full-dimensional ab initio potential energy surface and variational vibrational states

Abstract

ABSTRACT The automated development of a new ab initio full-dimensional potential energy surface (PES) is reported for the CH4·F− complex using the Robosurfer program package. The new potential provides a near-spectroscopic quality description over a broad configuration range including the methane-ion dissociation, as well as isolated methane vibrations. In particular, it improves upon the earlier [Czakó, Braams, Bowman (2008)] PES over intermediate methane-fluoride distances. Full-dimensional (12D) variational vibrational computations using the new PES and the GENIUSH-Smolyak algorithm show that tunnelling splittings larger than 0.1 cm−1 appear below the top of the interconversion barrier of the four equivalent minima of the complex.