| Research Abstract |
Three simulation methods, energy minimization, lattice dynamics, and molecular dynamics techniques, are often used to calculate structural and physical properties of minerals over wide temperature and pressure ranges. In this project, we prepared for general mineralogists to easily use the computer programs for the three methods. We further developed accurate interatomic potentials for use in computer simulation of Earth materials containing Na, Mg, Al, Si, K, Ca, and O ions by both empirical and non-empirical techniques.
In the empirical technique, the interionic potentials are taken to be the sum of pairwise additive Coulomb, van der Waals, and repulsive interactions, and many-body interactions in crystals. The breathing shell model is used to simulate the many-body forces, in which the repulsive radii of ions are allowed to deform isotropically under the effects of other ions in the crystal. Energy parameters were derived to accurately reproduce the observed structures, the measured thermal and elastic properties of rock-forming minerals including silicas, feldspars, pyroxenes and their polymorphs, olivines and their polymorphs, and some oxides.
In the non-empirical method, ab initio Hartree-Foxk self-consistent-field calculations were applied to model clusters composed of Mg, Si, and O ions, and effective interatomic potentials were obtained from the calculated potential energy surfaces of the model clusters. The first-principles path-integral molecular dynamics method is also used to simulate thermal properties.
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