Insight into the Hydration Mechanism of Illite Surfaces: A DFT Study
Tianyu Li1, Zhaoyun Chai1, Xiangyu Liu1
1Key Laboratory of In-Situ Property-Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan, Shanxi 030024, China.
The Journal of Physical Chemistry. B
|June 4, 2025
Summary
Water-sensitive clay minerals like illite significantly impact mud shale properties. This study reveals how water molecules interact with illite surfaces at a microscopic level, explaining macroscopic behaviors in geotechnical engineering.
Area of Science:
- Geochemistry
- Materials Science
- Computational Chemistry
Background:
- Water-sensitive clay minerals, particularly illite, are crucial in determining the physical properties of mud shale reservoirs.
- Macroscopic behaviors of mud shale, such as softening and loss of bearing capacity in wet conditions, stem from microscopic interactions between clay mineral unit cells and water.
- Understanding these water-clay interactions is vital for geotechnical and underground rock engineering applications.
Purpose of the Study:
- To systematically investigate the interaction mechanisms between water molecules and common exposed surfaces of illite using periodic density functional theory (DFT).
- To identify reactive sites, quantify adsorption energy, analyze charge transfer, and characterize bonding between water and illite surfaces ((001) and (001 bar)).
Main Methods:
- Application of periodic density functional theory (DFT) to model and analyze water molecule adsorption on illite surfaces.
- Calculation of adsorption energies, charge transfer, and bonding characteristics for water on illite (001) and (001 bar) surfaces.
- Identification of specific atomic sites and interactions governing water adsorption.
Main Results:
- Identified the most reactive sites for water adsorption on illite (001) as K+ ions and O atoms near Al3+ substitutions, and on illite (001 bar) as O atoms in surface silicon-oxygen rings.
- Confirmed stable adsorption of water molecules on both illite surfaces, with a preference for the (001) surface.
- Revealed distinct adsorption mechanisms: hydrogen bonding and electrostatic attraction on (001), and primarily hydrogen bonding on (001 bar), with charge transfer and interatomic bonding occurring on both.
Conclusions:
- The study elucidates the microscopic mechanisms of water-illite interactions, providing insights into the water sensitivity of mud shale.
- Preferential adsorption and differing interaction modes on illite (001) versus (001 bar) surfaces highlight the importance of surface structure in water-clay interactions.
- Findings contribute to a better understanding of mud shale behavior in geotechnical and underground engineering contexts.
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