Du Shiyu, Francisco Joseph S, Kais Sabre
Department of Chemistry, Purdue University, West Lafayette, Indiano 47907, USA.
J Chem Phys. 2009 Mar 28;130(12):124312. doi: 10.1063/1.3100549.
We present a study of electronic structure, stability, and dynamics of interaction and recombination of free radicals such as HO(2) and OH influenced by water. As simple model calculations, we performed ab initio and density functional calculations for the interaction of HO(2) and OH in the presence of water cluster. Results indicate that a significant interaction, overcoming the repulsive Columbic barrier, occurs at a separation distance between the radicals of 5.7 A. This confirms early predictions of the minimum size of molecular dianions stable in the gas phase. It is well known that atomic dianions are unstable in the gas phase but molecular dianions are stable when the size of the molecule is larger than 5.7 A. Ab initio molecular dynamics calculations with Car-Parrinello scheme show that the reaction is very fast and occurs on a time scale of about 1.5 ps. The difference in stability and dynamics of the interacting free radicals on singlet and triplet potential energy surfaces is also discussed.
我们展示了一项关于受水影响的自由基（如HO₂和OH）的电子结构、稳定性以及相互作用和重组动力学的研究。作为简单的模型计算，我们对水团簇存在下HO₂和OH的相互作用进行了从头算和密度泛函计算。结果表明，在自由基之间的分离距离为5.7埃时，发生了显著的相互作用，克服了排斥性的库仑势垒。这证实了早期关于气相中稳定分子双阴离子最小尺寸的预测。众所周知，原子双阴离子在气相中不稳定，但当分子尺寸大于5.7埃时，分子双阴离子是稳定的。采用Car-Parrinello方法的从头算分子动力学计算表明，该反应非常快，发生时间尺度约为1.5皮秒。还讨论了单重态和三重态势能面上相互作用自由基的稳定性和动力学差异。
