Applying Direct Molecular Dynamics to Non‐Adiabatic Systems
Applying Direct Molecular Dynamics to Non‐Adiabatic Systems
复制标题
将直接分子动力学应用于非绝热系统
DOI：
10.1002/0471433462.ch7
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
M. Robb
中科院分区：
文献类型：
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作者：
Graham A Worth;M. Robb
在大分子中，电子基态和第一激发态在许多核构型中是简并的。在这些被称为圆锥形交叉点的配置中，从电子激发态到基态的无辐射衰减是非常有效的。因此，锥形交叉点被认为在确定光化学反应的结果中是重要的。提出了一种定位它们的一般方法;它是基于Longuet-Higgins和Herzberg的相变规则。结果表明，使用该方法可以使多原子分子中圆锥相交的艰苦搜索系统化。总电子波函数的总相位变化，当传输围绕一个封闭的环路，是一个必要和充分的条件存在的圆锥形交叉内的环路。结果表明，一个方便的方法来确定回路是通过考虑基态表面上的基元化学反应引起的相变。每个圆锥交点由两个核坐标定义，导致简并点。这些坐标可以分配给两个不同的基元反应，通过它们三个不同的化学物种被连接起来。与热反应相反，光化学反应原则上需要沿沿着两个独立的坐标运动。通过沿着这些坐标的运动来消除简并性类似于导致Jahn-Teller效应中能量降低的畸变。这种方法的理论基础是多电子波函数的置换对称性。在此基础上，利用芳香性和反芳香性的概念，定义了伴随基元反应的相变。该方法有助于指导和集中基于计算机的搜索大分子的多维势面。
In large molecules, the electronic ground‐state and the first excited state are degenerate in many nuclear configurations. At these configurations, termed conical intersections, radiationless decay from the electronically excited state to the ground state is very efficient. Conical intersections are therefore believed to be important in determining the outcome of photochemical reactions. A general method for locating them is presented; it is based on the phase‐change rule of Longuet‐Higgins and Herzberg. It is shown that the arduous search for conical intersections in polyatomic molecules can be systemized using the method. The overall phase change of the total electronic wave function when transported adiabatically around a closed loop, is a necessary and sufficient condition for the existence of a conical intersection inside the loop. It is shown that a convenient method to determine the loop is by considering the phase change incurred by elementary chemical reactions on the ground‐state surface. Each conical intersection is defined by two nuclear coordinates leading to the degeneracy point. These coordinates can be assigned to two different elementary reactions, by which three distinct chemical species are connected. In contrast with thermal reactions, photochemical ones require in principle motion along two independent coordinates. The removal of the degeneracy by motion along these coordinates is analogous to the distortion leading to lowering the energy in the Jahn–Teller effect.The theoretical basis for this approach is the permutational symmetry of the polyelectronic wave function. The phase change accompanying an elementary reaction is defined on this basis, using the concepts of aromaticity and antiaromaticity. The method is helpful in directing and focusing computer‐based searches on the multidimensional potential surface of large molecules.