Long-range proton and hydroxide ion transfer dynamics at the water/CeO interface in the nanosecond regime: reactive molecular dynamics simulations and kinetic analysis

The structural properties, dynamical behaviors, and ion transport phenomena at the interface between water and cerium oxide are investigated by reactive molecular dynamics (MD) simulations employing neural network potentials (NNPs). The NNPs are trained to reproduce density functional theory (DFT) r...

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Published inChemical science (Cambridge) Vol. 15; no. 18; pp. 6816 - 6832
Main Authors Kobayashi, Taro, Ikeda, Tatsushi, Nakayama, Akira
Format Journal Article
Published 08.05.2024
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Summary:The structural properties, dynamical behaviors, and ion transport phenomena at the interface between water and cerium oxide are investigated by reactive molecular dynamics (MD) simulations employing neural network potentials (NNPs). The NNPs are trained to reproduce density functional theory (DFT) results, and DFT-based MD (DFT-MD) simulations with enhanced sampling techniques and refinement schemes are employed to efficiently and systematically acquire training data that include diverse hydrogen-bonding configurations caused by proton hopping events. The water interfaces with two low-index surfaces of (111) and (110) are explored with these NNPs, and the structure and long-range proton and hydroxide ion transfer dynamics are examined with unprecedented system sizes and long simulation times. Various types of proton hopping events at the interface are categorized and analyzed in detail. Furthermore, in order to decipher the proton and hydroxide ion transport phenomena along the surface, a counting analysis based on the semi-Markov process is formulated and applied to the MD trajectories to obtain reaction rates by considering the transport as stochastic jump processes. Through this model, the coupling between hopping events, vibrational motions, and hydrogen bond networks at the interface are quantitatively examined, and the high activity and ion transport phenomena at the water/CeO 2 interface are unequivocally revealed in the nanosecond regime. The structural properties, dynamical behaviors, and ion transport phenomena at the water/CeO 2 interface are investigated by reactive MD simulations employing NNPs, and a counting analysis based on the semi-Markov process is formulated and performed.
Bibliography:2
https://doi.org/10.1039/d4sc01422g
(111) and (110) interfaces. The proton hole trajectories are also shown as lines, with the colors corresponding to the transfer mechanisms as in
while the failed transports are also drawn as gray lines. See DOI
Electronic supplementary information (ESI) available: Details of enhanced sampling; construction and refinement of NNPs; molecular and dissociative adsorption of a water molecule; coverage as a function of time; representative snapshots of NNP-MD; radial distribution function of CeO; decomposed density profile at interfaces; supplementary figures of proton hopping mechanisms; proton assignment based on the SSP; lifetime histogram of transient ion species; details of cMSM and csMSM; parameters in KMC simulations; environment dependent reaction rates; time-dependent reaction rates of rattling events; vibrations of adsorbed species; combination between the SSP and cMSM/csMSM. Movies of representative 10 ps trajectories of the NNP-MD simulations at the water/CeO
Fig. 4(a)
ISSN:2041-6520
2041-6539
DOI:10.1039/d4sc01422g