A Mathematical Derivation of Geologically Important Silicate Minerals and a Study of Electron Density Distributions and the Nature of Bonds in Silicates

这个项目旨在推进三个领域的工作：矿物学、晶体学和地球化学。研究人员最近取得的进展导致了晶体结构、空间群对称性和细胞尺寸的确定。研究人员开发的软件利用量子力学计算产生的势能函数，推导出超过85种不同的稳定和亚稳态框架二氧化硅结构类型。对结构和推导中使用的势能函数的检查将提高对将结构结合在一起的力的理解，并阐明这些力在控制原子排列和所得到相的对称性方面所起的作用。计算还将提供结构类型的目录，这将有助于识别在实验室或自然界中发现的任何新结构类型。第一性原理晶体计算将用于生成本研究中衍生的新型低能结构类型的结构。预计这些信息将增加对势能和结构之间联系的理解，从而增强对结合力和电子密度分布在决定结构中所起作用的理解。将完成对各种羟基酸分子的键的电子密度分布的分析，试图将这些分子中键的分数离子特征与电子密度以及键临界点处的局部动能和势能密度联系起来。这项研究的一个好处是，它可能导致新的多孔构造硅酸盐合成模型和策略的改进，这些材料已被发现用于石油产品的选矿和生产。另一个好处是，计算可以产生具有6坐标Si的致密硅结构类型s的集合，这将在地球物理研究中具有重要意义。

9627458 Gibbs This project is designed to advance work in three fields: mineralogy, crystallography and geochemistry. Recent advances by the investigators have resulted in a determination of crystal structures, space group symmetries and cell dimensions. Software, developed by the investigators, was used to derive more than 85 distinct stable and metastable framework silica structure types employing a potential energy function created from quantum mechanical calculations. An examination of the structure and the potential energy functions used in the derivations will improve the understanding of the forces that bind the structures together and clarify the role that these forces play in governing the atomic arrangements and the symmetries of the resulting phases. The calculations will also provide a catalog of structure types that will facilitate the identification of any new structure types that are discovered either in the laboratory or in nature. First principle crystal calculations will be used to generate structures for the new low energy structure types derived in this study. It is anticipated that this information will increase the understanding of the connection between potential energy and structure thereby enhancing the understanding of the role that the binding forces and the electron density distributions play in determining structure. An analysis will be completed of the electron density distributions calculated for the bonds of a variety of hydroxyacid molecules in an attempt to relate the fractional ionic character of the bonds in these molecules to the electron density and the local kinetic and potential energy densities at the bond critical points. One of the benefits of this study is that it could lead to improved models and strategies for the synthesis of new porous tectosilicates, materials that have found use in the beneficiation and generation of petroleum products. Another benefit is that the calculations could produce a collection of dense silica structure type s with 6-coordinate Si, phases which would be of importance in geophysical research.