Atomic-scale to mesoscale simulation of mineral growth and dissolution reactions

Abstract

Rare event methods can potentially allow unprecedented ability to determine reaction mechanisms, rate and equilibrium constants for atomic-scale mineral growth and dissolution reactions. These in turn may allow one to develop more accurate and predictive macroscopic rate expressions. However, for any predicted reaction mechanisms to be realistic, the simulation must be calibrated and validated to experimental data that demonstrates that the model produces plausible chemical reactions. Such experimental data include traditional parameters such as the solubility product, ion hydration energies, and bulk mineral structure. This also includes new data such as the interfacial structure measured by X-ray Reflectivity, the interfacial dynamics measured by Quasi-Elastic Neutron Scattering, and aqueous ion hydration structure measured by Neutron Diffraction with Isotopic Substitution or X-ray pair distribution function analysis. More valid comparisons between experiments and the simulations are in active development to better gauge the consistency between simulation and experiment. Once derived, any plausible reaction mechanisms derived from the rare even theories must then be incorporated into mesoscale simulation approaches such as kinetic Monte Carlo to be compared to experimental measurements of mineral growth and dissolution, such as by atomic force microscopy. The focus of this talk will be on applying the methods discussed above to the growth of two sparingly-soluble salts, barite (BaSO4) and calcite (CaCO3).