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The group’s main interest is in understanding the mechanisms of chemical reactions. This pursuit involves the development of methods for constructing potential energy surfaces for chemical reactions and the reaction dynamics on these surfaces. Ab initio quantum chemistry provides accurate information about the electronic energy of a molecule for any geometry. The way that atoms move during a chemical reaction is determined by how the electronic energy changes as the shape of the molecule changes. To understand the mechanism of a chemical reaction (how the atoms move) we need to know the electronic energy for all the possible molecular shapes (which is a potential energy surface or PES). The PES is constructed as an interpolation of the ab initio data evaluated at a relatively small number of relevant molecular geometries. Significant progress has now been achieved for moderate sized molecules, so that many different chemical reactions have been investigated. Most of these reactions involve competing mechanisms or reaction pathways and could not be treated using simpler approximate methods. The end result of this work should be a much clearer understanding of the mechanisms of reaction at the molecular level. Our current work is concentrated in two main areas.
Michael Collins is the Associate Director of Students at the Research School of Chemistry.
Postdoctoral Fellows |
The method we have developed to approximate molecular energies has been applied to estimating the energies (and free energies) of crystals.
Ab initio electronic structure theory provides the practical means to calculate the total electronic energy of moderate-sized molecules.
The abstraction reactions, X• + RH' <-> XH + R•, where X = H, F or Cl, are important in many contexts, including combustion.
Many reactions, particularly in photochemistry, combustion, atmospheric and interstellar chemistry, take place in more than one electronic state.