# Autoionization in liquid water

Geissler, P L; Dellago, C; Chandler, D; Hutter, J; Parrinello, M (2001). Autoionization in liquid water. Science, 291(5511):2121-2124.

## Abstract

The dissociation of a water molecule in Liquid water is the fundamental event in acid-base chemistry, determining the pH of water. Because of the short time scales and microscopic length scales involved, the dynamics of this autoionization have not been directly probed by experiment. Here, the autoionization mechanism is revealed by sampling and analyzing ab initio molecular dynamics trajectories. We identify the rare fluctuations in solvation energies that destabilize an oxygen-hydrogen bond, Through the transfer of protons along a hydrogen bond wire'', the nascent ions separate by three or more neighbors. If the hydrogen bond wire connecting the two ions is subsequently broken, a metastable charge-separated state is visited. The ions may then diffuse to Large separations. If, however, the hydrogen bond wire remains unbroken. the ions recombine rapidly. Because of their concomitant Large electric fields, the transient ionic species produced in this case may provide an experimentally detectable signal of the dynamics we report.

The dissociation of a water molecule in Liquid water is the fundamental event in acid-base chemistry, determining the pH of water. Because of the short time scales and microscopic length scales involved, the dynamics of this autoionization have not been directly probed by experiment. Here, the autoionization mechanism is revealed by sampling and analyzing ab initio molecular dynamics trajectories. We identify the rare fluctuations in solvation energies that destabilize an oxygen-hydrogen bond, Through the transfer of protons along a hydrogen bond wire'', the nascent ions separate by three or more neighbors. If the hydrogen bond wire connecting the two ions is subsequently broken, a metastable charge-separated state is visited. The ions may then diffuse to Large separations. If, however, the hydrogen bond wire remains unbroken. the ions recombine rapidly. Because of their concomitant Large electric fields, the transient ionic species produced in this case may provide an experimentally detectable signal of the dynamics we report.

## Citations

412 citations in Web of Science®
410 citations in Scopus®

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Department of Chemistry 540 Chemistry English 2001 25 Mar 2009 16:25 05 Apr 2016 12:26 American Association for the Advancement of Science (AAAS) 0036-8075 10.1126/science.1056991 11251111
Permanent URL: http://doi.org/10.5167/uzh-3197

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