Ab Initio Electron-Gas Models With Polarizable Ions: Applications to Complex Minerals in the Transition Zone and Lower Mantle

9814304Bukowinski这是一个项目的延续，该项目使用密度泛函理论来开发自洽的从头算模型，以及有效的伪经验模型，可变形离子对晶体环境中压力和温度引起的变化的响应。 这些模型旨在通过提供准确且非常有效的技术来补充第一原理方法，这些技术能够模拟石榴石等复杂矿物，这些矿物仍然超出了完全第一原理方法的实际范围。 将包括球形和非球形变形，以及长程货车德瓦尔斯相互作用的影响。 该模型将包括，作为特殊情况下，目前的电子气体势理论。然后，充分发展的模型将被用来检查的静态和动态性质的过渡带和下地幔矿物组成的SiO2，MgO，FeO，CaO和Al2O3。 蒙特卡罗，分子动力学和模拟退火技术，将被用来探索矿物结构，可能会形成在中间和非常高的压力和温度，以及压力对结构的熔体与硅酸盐组合物的影响。 同样的方法将用于估计模拟矿物组合所需的热参数，这些矿物组合可能解释所观察到的地幔地震特性。新的模型还应允许检查的压力依赖性的离子极化率，以及晶体极化率和极化扩散，元素分区和IR和拉曼振幅的影响。 如果成功，新模型将在极端温度和压力条件下提供各种类型的实验数据和矿物和流体模型之间的联系。 扩大的认识和新的理论工具应能使人们更好地了解地球地幔中地震速度的径向不连续性、各向异性和横向不均匀性的可能来源，以及对地震速度和地球地球化学演变的热、结构和化学影响。该项目由岩石学、地球化学和地球物理学项目共同资助。

9814304BukowinskiThis is a continuation of a project that uses density functional theory to develop self-consistent ab initio models, as well as efficient pseudoempirical models, of the response of deformable ions to pressure andtemperature induced changes in crystal environments. These models are designed to complement first principles methods by providing accurate and yet very efficient techniques capable of simulating complex minerals like garnets that remain beyond the practical reach of fully first principles methods. Spherical and non-spherical deformations will be included, as well as the effects of long-ranged van der Waals interactions. The model will include, as special cases, current electron-gas potential theories. The fully developed models will then be used to examine the static and dynamic properties of transition zone and lower mantle minerals composed of SiO2, MgO, FeO, CaO and Al2O3. Monte Carlo, molecular dynamics and simulated annealing techniques, will be used to explore mineral structures that may form at ntermediate and very high pressures and temperatures, as well as the effects of pressure on the structure of melts with silicate compositions. The same methods will be used to estimate thermal parameters needed to model mineral assemblages that may account for the observed seismic properties of the mantle. The new models should also allow examination of the pressure dependence of ionic polarizabilities, as well as crystal polarizabilities and the effects of polarizability on diffusion, element partitioning and IR and Raman amplitudes. If successful, the new models stand to provide a link among various types of experimental data and models of minerals and fluids at extreme conditions of temperature and pressure. The expanded understanding and new theoretical tools should lead to a better understanding of possible sources of radial discontinuities, anisotropy and lateral heterogeneity of seismic velocities in the mantle of the Earth, and of thermal, structural and chemical effects on seismic velocities and the geochemical evolution of the earth. This project is jointly funded by the Petrology & Geochemistry and Geophysics Programs.