Theoretical Studies of Structure and Spectra of Glasses

玻璃结构与光谱的理论研究——从头算Hartree-Fock自洽场分子轨道理论水平上的量子化学方法将应用于玻璃科学中的许多问题。基本目标将是通过计算它们的几何、能量学和光谱值，并与实验进行比较，来表征玻璃杯中物种的中短期序列。将计算几种短程有序物质（如硼砂环和硅酸盐四面体）在玻璃中的各种物质的核磁共振谱。结构和光谱性质作为电荷状态和聚合程度的函数将被计算，以协助监测溶胶-凝胶反应。最后，将开发方法来计算在玻璃中发现的各种环境中的氧的极化率，并计算用于评估玻璃中不同氧化环境的光学碱度的自由和络合探针离子的光谱能量。该提案将由dmr -材料理论（67%）和chem -物理化学（33%）共同资助。人们曾经认为，晶体固体和玻璃固体在结构上有很大的不同，晶体既具有短程有序，也具有长程有序，而玻璃即使有秩序，也只是在局部水平上有意义。现在看来很清楚，在许多情况下，玻璃具有大量的中等范围秩序，即在长度尺度上对应于几个分子单位的秩序。增加对玻璃中存在的局部和中等范围秩序类型的了解，以及这种秩序对玻璃性质的影响，将使使用非经验原子方法制造具有定制性质的玻璃成为可能。将量子化学方法应用于该问题是本提案的目标，该提案将由dmr -材料理论（67%）和chem -物理化学（33%）共同资助。

Theoretical Studies of Structure and Spectra of Glasses - Quantum- chemical methods at the level of ab initio Hartree-Fock Self- Consistent Field Molecular Orbital Theory will be applied to a number of problems in glass science. The basic goal will be to characterize both the short and medium range order of species in glasses by calculating values for their geometries, energetics, and spectra, and comparing with experiment. NMR spectra of various species in glasses will be calculated for several short range ordered species, e.g., boroxol rings and silicate tetrahedra in their respective glasses. Structural and spectral properties as a function of charge state and degree of polymerization will be calculated to assist in monitoring sol-gel reactions. Finally, methods will be developed to calculate polarizabilities of oxygen in various environments found in glasses and to calculate spectral energies for free and complexed probe ions used to evaluate the optical basicities of different oxidic environments in glasses. This proposal will be cofunded by DMR-Materials Theory (67%) and by CHEM-Physical Chemistry (33%). %%% It was once thought that crystalline and glassy solids were very much different structurally, with crystalls possessing both short and long range order and glasses possessing order in any meaningful sense only at the local level if at all. It now seems clear that in many cases glasses possess substantial medium range order, i.e., order on a length scale corresponding to several molecular units. Increased knowledge of the types of local and medium range order existing in glasses and the influence of such order upon the properties of the glass will make it possible to create glasses with tailored properties using nonempirical atomistic approaches. Application of quantum chemical methods to this problem is the goal of this proposal, which will be cofunded by DMR-Materials Theory (67%) and by CHEM-Physical Chemistry (33%).