Dr. Sebastien Kerisit from Pacific Northwest National Lab will present a seminar entitled, “Molecular Mechanisms of Reactivity at Mineral-Water Interfaces.”

Host: David Dixon

Abstract:

This seminar will showcase examples of on-going research in the Geochemistry Group at Pacific Northwest National Laboratory focused on determining the molecular mechanisms responsible for mineral nucleation and growth in geochemical environments.

As a first example, the heteroepitaxial nucleation and growth of metal carbonate minerals will be discussed. Mineral surfaces serve as substrates for heterogeneous nucleation in aqueous solutions and can support the growth of heteroepitaxial coatings if the atomic arrangement of the substrate closely matches that of the nucleating phase. Heteroepitaxial coatings play an important role in understanding mineral surface reactivity as coatings of even nanometer scale can significantly affect some properties of the mineral-water interface. State-of-the-art experimental techniques such as atomic force microscopy, high-resolution transmission electron microscopy, and three-dimensional atom probe tomography were combined to elucidate the factors that control the nucleation and growth of heteroepitaxial coatings on carbonate single crystals.

The reactivity of caprock minerals with water-bearing supercritical carbon dioxide fluids (WBSF) will also be discussed as it is receiving increasing attention due to its relevance to the chemistry of carbon sequestration. In particular, divalent cation-rich silicate minerals such as olivines have a high potential for undergoing carbonation reactions, a process that can lead to long-term storage of carbon as carbonate minerals. Insights gained from computational techniques into the mechanisms of carbonation reactions in conditions relevant to geologic carbon sequestration will be presented in this seminar. Specifically, ab initio and classical molecular dynamics simulations were employed to investigate the structure and reactivity of interfaces between WBSF and a number of olivine minerals as a function of water content.