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Molecular Dynamics Simulations of the Hydrogen Peroxyl Radical

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Doctoral thesis

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The first study of this dissertation is focused on the classical dynamics and rates of isomerization and dissociation of HO2 have been studied using three potential energy surfaces PESs. The intramolecular vibrational energy redistribution IVR at energies above and below the threshold of isomerization is slow, especially for O O stretch excitations, consistent with the regularity in the surfaces-of-section. The slow IVR rates lead to mode-specific effects that are prominent for isomerization and modest for unimolecular dissociation to H O2. Even with statistical distributions of initial energy, slow IVR rates result in double exponential decay for isomerization, with the slower rate correlated with slow IVR rates for O--O vibrational excitation. The calculated IVR results for all three PESs are reasonably well represented by an analytic, coupled three-mode energy transfer model. The second study of this thesis is focused on the effects of pressure on the relaxation of the HO2 embedded in a dense gas environment. A method of simulating the radical in an argon bath is proposed and validated. The time dependent decay of vibrational energy is found to be biexponential for all of the simulated pressure. The relaxation rates at low pressures extrapolate poorly to the high pressures results with a turnover in the rates occurring at intermediate pressures. The effects of finite size effects on the simulation are investigated. Comparisons to studies with similar findings and additional considerations for understanding this behavior are discussed.

Subject Categories:

  • Inorganic Chemistry
  • Atomic and Molecular Physics and Spectroscopy
  • Combustion and Ignition

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