Journal
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
Volume 24, Issue 25, Pages 15365-15375Publisher
ROYAL SOC CHEMISTRY
DOI: 10.1039/d2cp01708c
Keywords
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Funding
- German National Academy of Sciences Leopoldina [LPDS 2020-05]
- UK National Supercomputing Service through an EPSRC Pioneer Project grant
- PRACE
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Metal oxide/water interfaces play a crucial role in various fields, but their atomistic structure is challenging to characterize experimentally. This study utilizes a neural network potential to simulate the dynamics at the hematite/water interface, revealing solvation dynamics and diffusion of water molecules.
Metal oxide/water interfaces play an important role in biology, catalysis, energy storage and photocatalytic water splitting. The atomistic structure at these interfaces is often difficult to characterize by experimental techniques, whilst results from ab initio molecular dynamics simulations tend to be uncertain due to the limited length and time scales accessible. In this work, we train a committee neural network potential to simulate the hematite/water interface at the hybrid DFT level of theory to reach the nanosecond timescale and systems containing more than 3000 atoms. The NNP enables us to converge dynamical properties, not possible with brute-force ab initio molecular dynamics. Our simulations uncover a rich solvation dynamics at the hematite/water interface spanning three different time scales: picosecond H-bond dynamics between surface hydroxyls and the first water layer, in-plane/out-of-plane tilt motion of surface hydroxyls on the 10 ps time scale, and diffusion of water molecules from the oxide surface characterized by a mean residence lifetime of about 60 ps. Calculation of vibrational spectra confirm that H-bonds between surface hydroxyls and first layer water molecules are stronger than H-bonds in bulk water. Our study showcases how state of the art machine learning approaches can routinely be utilized to explore the structural dynamics at transition metal oxide interfaces with complex electronic structure. It foreshadows that c-NNPs are a promising tool to tackle the sampling problem in ab initio electrochemistry with explicit solvent molecules.
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