【摘要】 过剩电子不仅是辐射破坏的重要根源,而且也参与诸如环丁烷嘧啶二聚体等辐射产物的修复过程.利用从头算分子动力学模拟,本工作再现了单电子分步催化环丁烷嘧啶二聚体离解的详细过程,特别获得了与过剩电子有关的能量和分子结构详细信息.基于垂直注入环丁烷嘧啶二聚体水溶液过剩双电子的分子动力学模拟,本文排除了早期建议的类[2+2]协同同步离解机理,分析了实际反应对称性与严重影响机理的轨道对称性的差别.重要的是,本文提出一个双电子分步催化离解机理新模型,可以合理解释反应实验观察.本工作不仅对电子催化离解机理提供了动态洞察性的解析,而且也揭示了两个过剩电子在两个键断裂步骤中的不同作用(促进或抑制).更多还原

【Abstract】 Excess electrons are not only an important source of radiation damage, but also participate in the repair process of radiation damage such as cyclobutane pyrimidine dimer(CPD). Using ab initio molecular dynamics(AIMD) simulations,we reproduce the single excess electron stepwise catalytic CPD dissociation process in detail with an emphasis on the energy levels and molecular structure details associated with excess electrons. On the basis of the AIMD simulations on the CPD aqueous solution with two vertically added excess electrons, we exclude the early-proposed [2+2]-like concerted synchronous dissociation mechanism, and analyze the difference between the symmetry of the actual reaction and the symmetry of the frontier molecular orbitals which deeply impact the mechanism. Importantly, we propose a new model of the stepwise electron-catalyzed dissociation mechanism that conforms to the reality.This work not only provides dynamics insights into the excess electron catalyzed dissociation mechanism, but also reveals different roles of two excess electrons in two bond-cleavage steps(promoting versus inhibiting).更多还原