The Calcite (104) Surface - Electrolyte Structure: A 3D Comparison of Surface X-Ray Diffraction and Simulations

Adsorption and incorporation of ions is known to influence the morphology and growth of calcite. Using surface X-ray diffraction, the interfacial structure of calcite in contact with CaCO3, MgCl2, CaCl2
and BaCl2 solutions was determined. All of these conditions yield a comparable interfacial structure,
meaning that there is no significant ion adsorption. This allows for the first time a thorough comparison in all three dimensions with state-of-the-art computer simulations, involving molecular dynamics
based on both DFT and two different force field models. Additionally, the simulated structures are
used to calculate the corresponding structure factors, which in turn are compared to those obtained
from experiment, thereby avoiding the need for fitting or subjective interpretation. In general, there
is a good agreement between experiment and the simulations, though there are some small discrepancies in the atomic positions, which lead to an inadequate fit of certain features characteristic of the
structure of water at the interface. Of the three simulation methods examined, the DFT results were
found to agree best with the experimental structure.