Insight into the interface between Fe₃O₄ (001) surface and water overlayers through multiscale molecular dynamics...

Area of Science:

• Surface Science
• Computational Chemistry
• Materials Science

Background:

• The interface between iron oxide surfaces and water is critical in geochemistry, catalysis, and materials science.
• Understanding water molecule behavior at these interfaces informs processes like corrosion and mineral dissolution.

Purpose of the Study:

• To investigate the structure and energetics of water adsorption on the Fe3O4 (001) surface.
• To compare the accuracy of Density-Functional Tight-Binding (DFTB) and Molecular Mechanics (MM) methods against hybrid functional (HSE06) calculations and experimental data.
• To model water multilayer formation and ordering at the Fe3O4 (001) surface.

Main Methods:

• Hybrid functional (HSE06) calculations for benchmarking.
• Density-Functional Tight-Binding (DFTB) for structural and energetic analysis of water adsorption and multilayer formation.
• Molecular Mechanics (MM) with Molecular Dynamics (MD) simulations for large-scale water multilayer modeling.
• Analysis of water orientation, hydrogen bonding, and structural ordering.

Main Results:

• DFTB accurately reproduces HSE06 results for water adsorption up to a monolayer.
• Molecular dynamics simulations reveal ordered water structures and hydrogen bond networks at the interface.
• MM-MD simulations of a 12 nm water layer show structuring extending up to 6-7 Å, consistent with DFTB trilayer models.
• Discrepancies between MM and DFTB highlight the need for improved MM parameterization for Fe-water interactions.

Conclusions:

• DFTB is a reliable method for studying water adsorption on Fe3O4 (001) surfaces.
• Water molecules exhibit significant ordering and hydrogen bonding near the Fe3O4 surface.
• MM simulations provide insights into thicker water layers but require refinement for accurate Fe-water interactions.