Ab Initio Optimized All-Atom Force Field for Vapor–Liquid Equilibria Simulation of Trifluoromethanesulfonyl Fluoride

Abstract

Trifluoromethanesulfonyl fluoride (CF₃SO₂F) has attracted great interest as a promising replacement gas for sulfur hexafluoride in view of its excellent dielectric performance. The electronic structures of CF₃SO₂F and a total of seven dimeric complexes have been characterized theoretically using the M06-2X density functionals with the basis set up to 5-ζ (aug-cc-pV5Z + d) and Grimme's D3 dispersion corrections, the coupled-cluster with single, double, and non-iterative triple energies extrapolated to the complete basis set limit, and the symmetry-adapted perturbation theory (SAPT). The dimeric binding energies are in the range of 1–3 kcal mol⁻¹, depending strongly on the relative orientations of the monomers. The dominant dimerization occurs via the concerted interactions between CF₃ and SO₂ groups. A classical all-atom force field has been developed successfully for CF₃SO₂F on the basis of the SAPT-calculated decomposition asymptotes of the dimeric complexes. The vapor–liquid coexistence equilibria have been predicted using the hybrid Gibbs ensemble Monte Carlo algorithm. Theoretical vapor pressures and boiling point of CF₃SO₂F are in good agreement with the latest experimental data. In comparison with perfluoronitrile, CF₃SO₂F is superior in terms of liquefaction temperature but inferior in both viscosity and thermal conductivity. The present work sheds new light on the use of CF₃SO₂F as a promising alternative to dielectric and refrigerant fluids.