Resolving Point Defects in the Hydration Structure of Calcite (10.4) with Three-Dimensional Atomic Force Microscopy.

Area of Science:

• Geochemistry
• Surface Science
• Materials Science

Background:

• Defects at mineral surfaces are hypothesized to influence interfacial processes like mineral dissolution and growth.
• Experimental verification requires high-resolution real-space methods, such as atomic force microscopy (AFM).
• Previous studies resolved defects at mineral-water interfaces in 2D AFM images but not the surrounding hydration structure.

Purpose of the Study:

• To experimentally investigate and visualize point defects at mineral-water interfaces.
• To analyze the perturbation of the hydration structure around point defects.
• To determine the spatial extent of hydration perturbations caused by surface defects.

Main Methods:

• Utilizing high-resolution 3D atomic force microscopy (AFM) to image mineral surfaces.
• Analyzing the hydration structure surrounding resolved point defects.
• Employing molecular dynamics simulations to corroborate experimental findings.

Main Results:

• Point defects on the calcite (10.4) surface were resolved using high-resolution 3D AFM.
• Hydration structure perturbations around point defects were observed up to the fifth hydration layer.
• The lateral extent of hydration perturbation was found to be approximately one unit cell.

Conclusions:

• High-resolution 3D AFM can visualize point defects and their effects on hydration structures at mineral-water interfaces.
• Surface defects significantly perturb the local hydration environment.
• Experimental findings align with molecular dynamics simulations, validating the observed phenomena.