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Hydroxyl radical and hydroxide ion in liquid water: a comparative electron density functional theory study
Peter Vassilev1, Manuel J Louwerse, Evert Jan Baerends
1Divisie Scheikunde, afd. Theoretische Chemie, Vrije Universiteit Amsterdam, De Boelelaan 1083, Amsterdam 1081 HV, The Netherlands. vassilev@few.vu.nl
The Journal of Physical Chemistry. B
|December 27, 2005
Summary
Density functional theory simulations reveal hydroxyl radical (OH) forms a distinct solvation complex in water. This challenges the established view of rapid OH diffusion via hydrogen exchange.
Area of Science:
- Computational Chemistry
- Physical Chemistry
- Chemical Physics
Background:
- Understanding the behavior of hydroxyl radical (OH) and hydroxide ion (OH-) in aqueous solutions is crucial for various chemical processes.
- Previous models suggest rapid diffusion of OH radicals in water, primarily through hydrogen exchange mechanisms.
Purpose of the Study:
- To investigate the solvation structures and diffusion mechanisms of the hydroxyl radical (OH) and hydroxide ion (OH-) in water using advanced computational methods.
- To compare the solvation behavior of the neutral OH radical with the anionic OH- species.
Main Methods:
- Performed ab initio density functional theory molecular dynamics (DFT-MD) simulations.
- Utilized the Becke-Lee-Yang-Parr (BLYP) exchange-correlation functional.
- Analyzed the structures of the solvation shells for both OH and OH- in water.
Main Results:
- The hydroxyl radical (OH) forms a well-defined solvation shell with four water molecules.
- Three water molecules hydrogen-bond to OH, while a fourth engages in hemibonding via a three-electron bond.
- The diffusion mechanism and activity of OH differ from OH-, with potential implications for established models.
Conclusions:
- The simulated solvation structure of OH suggests a more complex interaction than previously assumed.
- The findings indicate that the widely accepted model of rapid OH diffusion in water via hydrogen exchange may require re-evaluation.
- While the BLYP functional's tendency to overestimate hemibonding is noted, the results provide a new perspective on OH radical behavior in aqueous environments.