Molecular modelling of carbonate minerals: studies of growth and morphology

The aim of the work presented here is to develop a computer simulation technique which will predict the surface structure, the morphology and the rate of growth of carbonates. The technique is based on energy minimization in which all atom positions are varied until the lowest energy configuration is achieved. An important development is the incorporation of dynamics which is used to calculate the effect of temperature on the thermodynamic properties including heat capacities and free energies. The energies are calculated by using an interatomic potential based on the Born model of solids. Hence the surface structure is probed on the atomic scale. This also offers the possibility of investigating the influence of selected additives or impurities on the surface structure and the morphology. Thus having established that the technique can reliably model each surface of pure calcite, we have studied the effect of a range of additives including Li, Mg and phosphate: for example, the elucidation of the mechanism whereby phosphate inhibits nucleation. The success achieved to date shows that computer modelling can provide a valuable link between microscopic and bulk behaviour and gives us confidence in extending the technique to other carbonates.