水二聚体和六聚体的重排
Rearrangements of Water Dimer and Hexamer
摘要：
重排机制的水二聚体和笼形式的水六聚体的理论研究，特别是参考隧道分裂和光谱。用{ \it ab initio}方法计算了水二聚体的三个最低势垒重排，并与以前的约束计算结果进行了比较.受体隧穿途径不通过围绕受体的$C_2$轴的直接旋转进行，而是通过供体围绕氢键和受体的相关“摆动”的相对异步旋转进行。不同笼异构体的水六聚体之间的重排研究了两个经验势。实验观察到的三重态分裂可能是两个单供体，单受体单体的翻转和分叉重排的结果。二维量子计算的核动力学表明，离域超过一个笼异构体可能会发生，特别是在激发态。
英文摘要：
Rearrangement mechanisms of the water dimer and the cage form of the water hexamer are examined theoretically with particular reference to tunneling splittings and spectroscopy. The three lowest barrier rearrangements of the water dimer are characterized by {\it ab initio} methods and compared with the results of previous constrained calculations. The acceptor-tunneling pathway does not proceed via a direct rotation around the $C_2$ axis of the acceptor, but rather via relatively asynchronous rotation of the donor about the hydrogen bond and an associated `wag' of the acceptor. Rearrangements between different cage isomers of the water hexamer are studied for two empirical potentials. The experimentally observed triplet splittings may be the result of flip and bifurcation rearrangements of the two single-donor, single-acceptor monomers. Two-dimensional quantum calculations of the nuclear dynamics suggest that delocalization over more than one cage isomer may occur, especially in excited states.
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