| Traditionally minerals were studied empirically, however for over a decade modern theoretical solid state physics has become part of the foundation of mineralogy and geophysics. Crystalline structures' behavior of Earth materials under extreme conditions of pressure and temperature now is understood in atomistic nonempirical terms. In this thesis we study the effect of iron on the structural and elastic properties of the three main constituents of the Earth's interior between ∼40 km and 660 km depth: olivine, wadsleyite and ringwoodite-(Mg,Fe)2SiO4. We apply density functional theory (DFT) within the local density approximation (LDA) and we use norm-conserving and ultrasoft pseudopotentials to study their static properties. Then we combine density functional perturbation theory (DFTP) and the quasiharmonic approximation to incorporate thermal effects well below the melting temperature of these minerals. Our predictions are found in very good agreement with available experimental data of these three minerals. We further investigate the role of composition in two seismic discontinuities associated with the transformations of olivine to wadsleyite and wadsleyite to ringwoodite near 410 and 520 km depth, respectively. |
