Quantum Calculations On Hydrogen Bonds In Certain Water Clusters Show Cooperative Effects.
Quantum Calculations On Hydrogen Bonds In Certain Water Clusters Show Cooperative Effects.
复制标题
对某些水团簇中氢键的量子计算显示出协同效应。
DOI：
10.1021/ct600139d
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发表时间：
2007
影响因子：
5.5
通讯作者：
Green,MichaelE
中科院分区：
文献类型：
--
作者：
Znamenskiy,VasiliyS;Green,MichaelE
裂隙和小团簇中的水分子与散装水中的水分子处于明显不同的环境中。我们已经进行了从头计算，证明了这一点在一系列的集群，表明合作效应必须考虑到在这样的有界系统中的氢键和水簇的治疗。在模拟中，水分子之间的氢键最常使用点电荷水电位（如TIP3P或SPC）来处理，有时还使用可极化的扩展。它们在散装水中产生出色的结果，并为此进行校准。裂缝与体积不同;有必要研究较小的系统并研究有限数量邻居的影响。我们首先研究了孤立的水分子团簇，这些水分子团簇具有不同数量的氢键水分子对的邻居。整个集群处于真空状态。定义的集群，以便提供一个中心的氢键对水分子的最近邻居的可能的安排。然后，我们扫描的长度和角度的簇的中心氢键，使用密度泛函理论，为每个可能的安排的供体和受体氢键上的中心氢键对;两个水分子的相互作用的潜力随供体和受体邻居的数量而变化。这还涉及水分子上的电荷作为键长的函数的变化以及能量和长度作为相邻供体和受体分子的数量的函数的变化。当键长单独变化时，能量从最高到最低在室温附近变化约6kBT，足以严重影响模拟。
Water molecules in clefts and small clusters are in a significantly different environment than those in bulk water. We have carried out ab initio calculations that demonstrate this in a series of clusters, showing that cooperative effects must be taken into account in the treatment of hydrogen bonds and water clusters in such bounded systems. Hydrogen bonds between water molecules in simulations are treated most frequently by using point-charge water potentials, such as TIP3P or SPC, sometimes with a polarizable extension. These produce excellent results in bulk water, for which they are calibrated. Clefts are different from bulk; it is necessary to look at smaller systems and investigate the effect of limited numbers of neighbors. We start with a study of isolated clusters of water with varying numbers of neighbors of a hydrogen-bonded pair of water molecules. The cluster as a whole is in a vacuum. The clusters are defined so as to provide the possible arrangements of nearest neighbors of a central hydrogen-bonded pair of water molecules. We then scan the length and angles of the central hydrogen bond of the clusters, using density functional theory, for each possible arrangement of donor and acceptor hydrogen bonds on the central hydrogen-bonding pair; the potential of interaction of two water molecules varies with the number of donor and acceptor neighbors. This also involves changes in charge on the water molecules as a function of bond length and changes in energy and length as a function of the number of neighboring donor and acceptor molecules. The energy varies by approximately 6kBTnear room temperature from the highest to the lowest energy when bond length alone is varied, enough to seriously affect simulations.