Atomistic Simulation of Mineral Surfaces

Abstract

Atomistic simulation techniques are now able to model the structure of mineral surfaces at the atomic level. In this paper we begin to address the question of whether surface reactivity can be studied reliably by modelling the surface reactivity of calcite, fluorite and forsterite under aqueous conditions. We first used energy minimisation techniques to investigate the interaction between the minerals calcite and fluorite with water and methanoic acid. The relative adsorption energies suggest that methanoic acid preferentially adsorbs onto fluorite surfaces, while water adsorbs preferentially onto calcite as inferred from experiments on mineral separation. Molecular Dynamics simulations were also used to model the effect of temperature on the adsorption of water on the calcite {1014} and fluorite {111} surfaces. Furthermore we used these techniques to model point defect formation at surfaces. We are also interested in modelling the competition between associative and dissociative adsorption on mineral surfaces. Simulations of adsorption of water on the low-index forsterite surfaces have predicted the adsorption energies and equilibrium morphology. The calculated equilibrium morphology adequately reproduces the experimental morphology of forsterite suggesting that the relative stabilities of the surfaces, both unhydrated and hydroxylated, are calculated correctly.

Key Words:

• Mineral surfaces
• low-index
• fluorite surfaces
• cleavage planes
• energy minimization