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首页> 外文OA文献 >COMPUTATIONAL STUDIES OF CHEMICAL SYSTEMS: I. A THEORETICAL INVESTIGATION OF CLATHRATE HYDRATESII. CONFORMATIONAL POTENTIAL ENERGY SURFACE OF TRYPTAMINE
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COMPUTATIONAL STUDIES OF CHEMICAL SYSTEMS: I. A THEORETICAL INVESTIGATION OF CLATHRATE HYDRATESII. CONFORMATIONAL POTENTIAL ENERGY SURFACE OF TRYPTAMINE

机译：化学体系的计算研究：I.包合物水合物的理论研究II。氨胺的构象势能面

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Hydrogen clathrates have recently been discovered and considered as storage medium for H2. Hydrogen forms a Type II clathrate structure, with a small and large cage. Multiple guest hydrogen molecules can occupy both cages (up to two in the small cage and four in the large cage), although the number of hydrogen molecules occupying the small cage has been a source of debate in the literature. The goal of this work has been to develop a polarizable force field for use in molecular dynamics simulations of hydrogen clathrates. The resulting force field has been coded in the DLPOLY package and simulations of the system as a function of the number of guest hydrogen molecules have been performed. The development of the force field, and the results of the simulations are discussed.In order for a clathrate structure to form, a 'guest' molecule must be present under ideal conditions. That is, water does not form a so-called 'self' hydrate. In order to elucidate the factors responsible for clathrate formation, emph{ab initio} calculations were performed on (H2O)$_{21}$ and (H2O)$_{20}$*H2S clusters. The results of these calculations have provided insight into why water does not form a self hydrate.Stimulated emission pumping experiments done by the Zwier group have established bounds on the low energy isomerization barriers between specific minima of tryptamine. In order to identify the low energy isomerization pathways, the Becke3LYP and RI-MP2 methods were used to characterize the low-energy minima and the transition states of tryptamine. In general there is good agreement between theory and experiment, but for a subset of the isomerization processes, the calculations give significantly higher barriers than deduced from experiment. Possible causes of this discrepancy are discussed.
机译：氢包合物最近被发现并被认为是氢气的存储介质。氢形成II型笼形结构，并具有大小不一的笼子。多个客体氢分子可以同时占据两个笼子（小笼子中最多两个，大笼子中最多四个），尽管占据小笼子的氢分子的数量一直是文献中争论的焦点。这项工作的目的是开发一种极化极化力场，用于氢包合物的分子动力学模拟。合成的力场已在DLPOLY软件包中进行了编码，并且已根据来宾氢分子的数量对系统进行了仿真。讨论了力场的发展以及仿真结果。为了形成笼形结构，在理想条件下必须存在一个“客体”分子。也就是说，水不会形成所谓的“自身”水合物。为了阐明导致包合物形成的因素，对（H2O）$ _ {21} $和（H2O）$ _ {20} $ * H2S团簇进行了emph {ab initio}计算。这些计算的结果提供了洞悉水为什么不形成自水合物的真知灼见。Zwier研究小组进行的受激发射泵浦实验已经确定了色胺特定最小值之间的低能异构化障碍。为了确定低能异构化途径，使用Becke3LYP和RI-MP2方法表征了低能最小值和色胺的过渡态。通常，理论与实验之间有很好的一致性，但是对于异构化过程的一个子集，计算得出的壁垒比实验得出的要高得多。讨论了这种差异的可能原因。

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    McCarthy Valerie Nicole;

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  • 年度 2008
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