A computer simulation approach to modelling the structure,thermodynamics and oxygen isotope equilibria of silicates

We use an atomistic model to simulate the structure, lattice dynamics and thermodynamics of silicate minerals. Our approach uses the Born model of a solid, in which the interaction between atoms is described by an interatomic pair potential. We have extended the study of thermodynamics to its very limit by looking at the subtle reaction of oxygen isotope exchange. We have modelled equilibria involving the important metamorphic minerals; albite, diopside, forsterite, pyrope, quartz and wollastonite. The predicted structural and thermodynamic data for these silicates are in very good agreement with the observed values. In addition, we predict not only the correct direction for the phase equilibria for oxygen isotope exchange, but also fractionation factors for the reaction to within a factor of two of the available experimental data. Hence, the potentials used in our approach have shown excellent transferability and have performed very well against the most stringent of tests.