Ardalan Hayatifar^1*, Simon Gravelle^2*, Beatriz D. Moreno^3*, Valerie A. Schoepfer^1*, Matthew B. J. Lindsay^1*

1 Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada

2 University Grenoble Alpes, CNRS, LIPhy, 38000, Grenoble, France

3 Science Division, Canadian Light Source, Saskatoon, SK, Canada

* Corresponding authors emails: ardalan.hayatifar@usask.ca, simon.gravelle@cnrs.fr, Beatriz.Moreno@lightsource.ca, valerie.schoepfer@usask.ca, matt.lindsay@usask.ca

DOI10.24435/materialscloud:vc-ch [version v1]

Publication date: Feb 19, 2025

How to cite this record

Ardalan Hayatifar, Simon Gravelle, Beatriz D. Moreno, Valerie A. Schoepfer, Matthew B. J. Lindsay, Probing atomic-scale processes at the ferrihydrite-water interface with reactive molecular dynamics, Materials Cloud Archive 2025.29 (2025), https://doi.org/10.24435/materialscloud:vc-ch

Description

Interfacial processes involving metal (oxyhydr)oxide phases are important for the mobility and bioavailability of nutrients and contaminants in soils, sediments, and water. Consequently, these processes influence ecosystem health and functioning, and have shaped the biological and environmental co-evolution of Earth over geologic time. Here we employ reactive molecular dynamics simulations, supported by synchrotron X-ray spectroscopy to study the molecular-scale interfacial processes that influence surface complexation in ferrihydrite-water systems containing aqueous molybdate. We validate the utility of this approach by calculating surface complexation models directly from simulations. The reactive force-field captures the realistic dynamics of surface restructuring, surface charge equilibration, and the evolution of the interfacial water hydrogen bond network in response to adsorption and proton transfer. We find that upon hydration and adsorption, ferrihydrite restructures into a more disordered phase through surface charge equilibration, as revealed by simulations and high-resolution X-ray diffraction. We observed how this restructuring leads to a different interfacial hydrogen bond network compared to bulk water by monitoring water dynamics. Using umbrella sampling, we constructed the free energy landscape of aqueous molybdate adsorption at various concentrations and the deprotonation of the ferrihydrite surface. The results demonstrate excellent agreement with the values reported by experimental surface complexation models. These findings are important as reactive molecular dynamics opens new avenues to study mineral-water interfaces, enriching and refining surface complexation models beyond their foundational assumptions.

Materials Cloud sections using this data

Files

File name	Size	Description
Mo-9_simulation.mp4 MD5md5:07e9b5e15ec6a1dc68767f17f8beefb1	2.7 MiB	Trajectory of Mo-9 system
trajectories_analysis_scripts.zip MD5md5:f750de326ce1f2de22fb5fded88b3072	31.7 MiB	The zip file contains short trajectories and analysis scripts

License

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External references

Keywords

Adsorption Umbrella sampling Synchrotron X-ray Pair distribution function Surface complexation models Ferrihydrite