Theoretical Studies of Structure and Spectra of Glasses

玻璃结构和光谱的理论研究--从头算Hartree-Fock自洽场水平上的量子化学方法分子轨道理论将应用于玻璃科学中的一些问题。基本目标将是通过计算它们的几何、能量和光谱的值，并与实验进行比较，来表征玻璃中物种的短程和中程有序。将计算玻璃中各种物种的核磁共振谱，包括几个短程有序物种，例如它们各自玻璃中的硼氧环和硅酸盐四面体。结构和光谱性质将作为电荷状态和聚合度的函数进行计算，以帮助监测溶胶-凝胶反应。最后，将开发计算玻璃中各种环境中氧的极化率的方法，以及计算自由和络合探测离子的光谱能量的方法，用于评估玻璃中不同氧化环境的光学碱性。这项提议将由DMR-材料理论(67%)和CHEM-物理化学(33%)共同资助。曾经认为晶体和玻璃固体在结构上有很大的不同，晶体具有短程和长程有序性，而玻璃具有任何有意义的意义上的有序性，如果有的话，只在局部水平上具有有序性。现在似乎很清楚，在许多情况下，玻璃具有相当大的中程有序，即与几个分子单元相对应的长度尺度上的有序。对玻璃中存在的局域和中程有序类型以及这种有序对玻璃性质的影响的了解的增加将使使用非经验原子学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这个问题是这项提案的目标，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%).