“The eSSENCE of COMPUTATIONAL CHEMISTRY & PHYSICS”

The seminar in the series “The eSSENCE of COMPUTATIONAL CHEMISTRY&PHYSICS” took place Wednesday 28 March.

Title:       “Molecular dynamics of the challenging OH* radical in aqueous environments”
Speaker:  Professor Peter G Kusalik, University of Calgary, Alberta, Canada
Place:       Ångström, Beurlingrummet
 
 Abstract: This talk deals with the computer exploration of structure, mobility and reactivity of hydroxyl radical (OH*) in aqueous environments. Results from direct simulations, from constrained and metadynamics, and from gas phase benchmarking calculations will be presented. Implications for effective potentials for modeling OH* in aqueous environments will also be discussed.

         The behaviour of OH* in aqueous environments is crucial to its role in various important reactions within or at the surfaces of water and ice. The OH* is a key chemical species that appears across a diverse range of fields such as atmospheric chemistry, cosmic and nuclear reactions, and the biomolecular mechanisms of aging and diseases such as cancer, for example. OH* has proven to be a very challenging species to investigate because of its highly reactive nature. Here I will report insights into the behaviour of the hydroxyl radical in water and in ice through, primarily, Car-Parrinello molecular dynamics simulations.           

         The reactivity, stability and mobility of OH*, and its relationship to local structure, will be discussed. I will demonstrate that the hydrogen atom transfer between OH* and a water molecule has a relatively small free energy barrier and follows an apparent hybrid (electron-proton transfer) mechanism in which local structural fluctuations play an important role. Details of the reactions and interactions that can occur between two OH* in water will be presented, where the production of an aqueous oxygen atom, O(aq), in the triplet state is observed. I will also show that two-center three-electron (“hemi-bond”) interactions play a crucial role in the behaviour of OH* in water and ice, particularly when there is a constrained hydrogen-bonding environment.   

Kersti Hermansson and Peter Broqvist. Structural Chemistry, Ångström

kersti@kemi.uu.se;
peter.broqvist@kemi.uu.se

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