Modelling silicate mineral interfaces for carbon dioxide sequestration: structure and stability of orthoenstatite...

Area of Science:

• Geochemistry
• Materials Science
• Computational Chemistry

Background:

• Orthoenstatite (Mg2Si2O6) is a silicate mineral relevant to geological CO2 sequestration.
• Understanding mineral surface behavior is crucial for carbon capture and storage (CCS) technologies.
• The atomic structure and stability of orthoenstatite surfaces were previously unexplored.

Purpose of the Study:

• To investigate the atomic structure and stability of orthoenstatite surfaces.
• To identify the primary stable surfaces of orthoenstatite.
• To understand surface reconstruction mechanisms relevant to CO2 interactions.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Classical rigid-ion force field modeling.
• Analysis of non-polar stoichiometric surfaces, focusing on {210}, {010}, {100}, {110}, and {120} facets.

Main Results:

• Identified three main stable orthoenstatite surfaces: {210}, {010}, and {100}.
• The {100} surface, frequently cited in literature, is the most unstable.
• Observed significant surface reconstruction on the {100} surface involving magnesium atom rearrangement and coordination changes.

Conclusions:

• The {100} surface reconstruction, influenced by the chemical environment (e.g., hydroxylation or phyllosilicate formation), affects its reactivity.
• Provides foundational knowledge for modeling CO2 reduction at enstatite-gas interfaces.
• Enables the development of future models for enstatite-liquid interfaces in CO2 capture contexts.