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

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.

GRAPHICAL ABSTRACT

KEYWORDS:

• ab initio potential energy surface
• Robosurfer
• spectroscopy
• variational vibrational computations
• tunnelling splittings

Acknowledgements

The work of GC, DP, and VT at the University of Szeged was supported by the National Research, Development and Innovation Office−NKFIH, K-125317; the Ministry of Human Capacities, Hungary grant 20391-3/2018/FEKUSTRAT; Project no. TKP2021-NVA-19, provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-NVA funding scheme; and the Momentum (Lendület) Program of the Hungarian Academy of Sciences. EM and GA thank the financial support of the Swiss National Science Foundation (PROMYS Grant, No. IZ11Z0 166525).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Swiss National Science Foundation (PROMYS Grant) [grant number IZ11Z0 166525]; National Research, Development and Innovation Office−NKFIH [grant number K-125317]; Momentum (Lendület) Program of the Hungarian Academy of Sciences; Ministry of Human Capacities, Hungary [grant number 20391-3/2018/FEKUSTRAT]; Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund [grant number TKP2021-NVA-19].