MOLECULAR MODELING 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 an d the rate of growth of carbonates. The technique is based on energy m inimization in which all atom positions are varied until the lowest en ergy configuration is achieved. An important development is the incorp oration of dynamics which is used to calculate the effect of temperatu re on the thermodynamic properties including heat capacities and free energies. The energies are calculated by using an interatomic potentia l based on the Born model of solids. Hence the surface structure is' p robed on the atomic scale. This also offers the possibility of investi gating the influence of selected additives or impurities on the surfac e structure and the morphology. Thus having established that the techn ique 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 an d gives us confidence in extending the technique to other carbonates.