Atomistic Simulation Studies of Mineral Surfaces and the Role of Impurities on Their Structure and Stability

Abstract

The aim of our current work is to predict the structure and stability of mineral surfaces. A major difficulty when comparing with the limited experimental data is that surface properties are often dominated by impurities which segregate to the surface. Thus we must also determine the extent to which different impurities segregate and their effect on the surface structure and stability. The approach we have adopted is to use atomistic simulation where the interaction between each atom is described by parameterised potential functions based on the Born model of solids. Once the total interaction energy is obtained, energy minimisation is used to determine the structure and stability of each surface. We illustrate these methods by describing work on three minerals. (1) MgAI204 (spinel) where the surface structures of the pure material are calculated to be different from the bulk (2) quartz where the surface structures and stabilities are modified by the presence of dissociatively adsorbed water. (3) CaCO3 where impurities segregating to the surfaces can dramatically modify the surface stability. This is best visuallsed by consider ing the simulated equil ibrium morphologies where the enhanced stability of certain crystal faces cause them to be expressed in the crystal habit.