Solvation Species of Hydrated Excess Protons in Liquid Water*

Solvation structures of excess protons in water are highly relevant to electric properties and for an understanding of proton transport in liquids and membranes. We present unprecedented long-time ab-initio molecular dynamics simulations using a state-of-the-art hybrid-meta GGA exchange-correlation functional to simulate the temporal evolution of an excess proton in liquid water. The functional yields excellent results for bulk water and results are compared to the state-of-the-art hybrid GGA functional rev-PBE0-D3. Our simulations suggest that protons in water are predominantly solvated within dimeric water structures and how the dimeric water solvation structure interacts with its closest water neighbor in a H₇O₃⁺ unit without persistent proton localization on a single water molecule. The findings are in close agreement with previous reports on water-ACN solvent mixtures [1,2] and unravel microscopic aspects of the asymmetric potential along the proton transfer coordinate observed in nonlinear two-dimensional infrared spectroscopy [3].

 

[1] Dahms et al., Science. 357, 491-495 (2017).

[2] Kundu et al., J. Phys. Chem. Lett. 10, 2287–2294 (2019).

[3] Fournier et al., Nat. Chem. 10, 932-937 (2018).