Molecular dynamics simulations of solvation and kink site formation at the {001} barite-water interface

Solvation and kink site formation on step edges are known to be controlling parameters in crystal growth and dissolution. However, links from classical crystal growth models to specific reactions at the mineral-water interface have remained elusive. Molecular dynamics is used here to examine the water structure on barium surface sites and kink site formation enthalpies for material adsorbed to and removed from the step parallel to the [120] direction on the {001} barite-water interface. The bariums at the interface are shown to be coordinatively unsaturated with respect to water, and it is suggested that this is due to a steric hindrance from the nature of the interface. Kink site detachment energies that include hydration energies are endothermic for barium and exothermic for sulfate. The implications and problems of using these parameters in a crystal growth model are discussed.