Molecular dynamics (MD) simulations were used to investigate the structure and lifetimes of hydrogen bonds and auto dissociation via proton transfer in bulk water using a reactive and dissociative all-atom potential that has previously been shown to match a variety of water properties and proton transfer. Using the topological model, each molecule's donated and accepted hydrogen bonds were labeled relative to the other hydrogen bonds on neighboring waters, providing a description of the effect of these details on the structure, dynamics and autoionization of water molecules. In agreement with prior data, asymmetric bonding at the sub-100 femtosecond timescale is observed, as well as the existence of linear, bifurcated, and dangling hydrogen bonds. The lifetime of the H-bond, 2.1 ps, is consistent with experimental data, with short time librations on the order of femtoseconds. The angular correlation functions, the presence of a second shell water entering the first shell, and OH vibrational stretch frequencies were all consistent with experiment or ab initio calculations. The simulations show short-lived (femtoseconds) dissociation of a small fraction of water molecules followed by rapid recombination. The role of the other H-bonds to the acceptor and on the donor plays an important part in proton transfer betweenmore »
Structural and dynamic properties of solvated hydroxide and hydronium ions in water from ab initio modeling
Predicting the asymmetric structure and dynamics of solvated hydroxide and hydronium in water from ab initio molecular dynamics (AIMD) has been a challenging task. The difficulty mainly comes from a lack of accurate and efficient exchange–correlation functional in elucidating the amphiphilic nature and the ubiquitous proton transfer behaviors of the two ions. By adopting the strongly constrained and appropriately normed (SCAN) meta-generalized gradient approximation functional in AIMD simulations, we systematically examine the amphiphilic properties, the solvation structures, the electronic structures, and the dynamic properties of the two water ions. In particular, we compare these results to those predicted by the PBE0-TS functional, which is an accurate yet computationally more expensive exchange–correlation functional. We demonstrate that the general-purpose SCAN functional provides a reliable choice for describing the two water ions. Specifically, in the SCAN picture of water ions, the appearance of the fourth and fifth hydrogen bonds near hydroxide stabilizes the pot-like shape solvation structure and suppresses the structural diffusion, while the hydronium stably donates three hydrogen bonds to its neighbors. We apply a detailed analysis of the proton transfer mechanism of the two ions and find the two ions exhibit substantially different proton transfer patterns. Our AIMD simulations indicate that more »
- Award ID(s):
- 2053195
- Publication Date:
- NSF-PAR ID:
- 10401308
- Journal Name:
- The Journal of Chemical Physics
- Volume:
- 157
- Issue:
- 2
- Page Range or eLocation-ID:
- 024503
- ISSN:
- 0021-9606
- Sponsoring Org:
- National Science Foundation
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