title: The Reaction between Bromine and the Water Dimer and the Highly Exothermic Reverse Reaction.
abstract: The entrance complex, transition state, and exit complex for the bromine atom plus water dimer reaction Br + (H2O)2 → HBr + (H2O)OH and its reverse reaction have been investigated using the CCSD(T) method with correlation consistent basis sets up to cc-pVQZ-PP. Based on the CCSD(T)/cc-pVQZ-PP results, the reaction is endothermic by 31.7 kcal/mol. The entrance complex Br⋯(H2O)2 is found to lie 6.5 kcal/mol below the separated reactants. The classical barrier lies 28.3 kcal/mol above the reactants. The exit complex HBr⋯(H2O)OH is bound by 6.0 kcal/mol relative to the separated products. Compared with the corresponding water monomer reaction Br + H2 O → HBr + OH, the second water molecule lowers the relative energies of the entrance complex, transition state, and exit complex by 3.0, 3.8, and 3.7 kcal/mol, respectively. Both zero-point vibrational energies and spin-orbit coupling effects make significant changes to the above classical energetics. Including both effects, the predicted energies relation to separated Br + (H2O)2 are -3.0 kcal/mol [Br···(H2O)2 ], 28.2 kcal/mol [transition state], 26.4 kcal/mol [HBr···(H2O)OH], and 30.5 kcal/mol [separated HBr + (H2O)OH]. The potential energy surface for the Br + (H2O)2 reaction is related to that for the valence isoelectronic Cl + (H2O)2 system but radically different from the F + (H2O)2 system.
authors.affiliation: MOE Key Laboratory of Theoretical Chemistry of the Environment, Center for Computational Quantum Chemistry, South China Normal University, Guangzhou, 510006, China.|Guangzhou Key Laboratory of Materials for Energy Conversion and Storage, School of Chemistry and Environment, South China Normal University, Guangzhou, 510006, China.|Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia, 30602.
authors.forename: Guoliang
authors.initials: G
authors.lastname: Li
authors.affiliation: MOE Key Laboratory of Theoretical Chemistry of the Environment, Center for Computational Quantum Chemistry, South China Normal University, Guangzhou, 510006, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.affiliation: MOE Key Laboratory of Theoretical Chemistry of the Environment, Center for Computational Quantum Chemistry, South China Normal University, Guangzhou, 510006, China.
authors.forename: Qian-Shu
authors.initials: QS
authors.lastname: Li
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia, 30602.
authors.forename: Yaoming
authors.initials: Y
authors.lastname: Xie
authors.affiliation: Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia, 30602.
authors.forename: Henry F
authors.initials: HF
authors.lastname: Schaefer
keywords: CCSD(T) computations; atom-molecule reactions; bromine atom; potential energy profile; water dimer