Probing the Local Structure of Liquid Water by X-ray Absorption Spectroscopy

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• 作者：Jared D. Smith ; Christopher D. Cappa ; Benjamin M. Messer ; Walter S. Drisdell ; Ronald C. Cohen ; Richard J. Saykally
• 刊名：Journal of Physical Chemistry B
• 出版年：2006
• 出版时间：October 12, 2006
• 年：2006
• 卷：110
• 期：40
• 页码：20038 - 20045
• 全文大小：349K
• 年卷期：v.110,no.40(October 12, 2006)
• ISSN：1520-5207

文摘

It was recently suggested that liquid water primarily comprises hydrogen-bonded rings and chains, as opposedto the traditionally accepted locally tetrahedral structure (Wernet et al. Science 2004, 304, 995). Thiscontroversial conclusion was primarily based on comparison between experimental and calculated X-rayabsorption spectra (XAS) using computer-generated ice-like 11-molecule clusters. Here we present calculationswhich conclusively show that when hydrogen-bonding configurations are chosen randomly, the calculatedXAS does not reproduce the experimental XAS regardless of the bonding model employed (i.e., rings andchains vs tetrahedral). Furthermore, we also present an analysis of a recently introduced asymmetric waterpotential (Soper, A. K. J. Phys.: Condens. Matter 2005, 17, S3273), which is representative of the rings andchains structure, and make comparisons with the standard SPC/E potential, which represents the locallytetrahedral structure. We find that the calculated XAS from both potentials is inconsistent with the experimentalXAS. However, we also show the calculated electric field distribution from the rings and chains structure isstrongly bimodal and highly inconsistent with the experimental Raman spectrum, thus casting serious doubton the validity of the rings and chains model for liquid water.