Mori Toshifumi, Martínez Todd J
PULSE Institute and Department of Chemistry, Stanford University, Stanford, California 94305, United States.
SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States.
J Chem Theory Comput. 2013 Feb 12;9(2):1155-63. doi: 10.1021/ct300892t. Epub 2013 Jan 22.
Conical intersections (CIs) play a fundamental role in photoreactions. Although it is widely known that CIs are not isolated points but rather multidimensional seams, there is a dearth of techniques to explore and characterize these seams beyond the immediate vicinity of minimum energy points within the intersection space (minimum energy conical intersections or MECIs). Here, we develop a method that connects these MECIs by minimal energy paths within the space of geometries that maintain the electronic degeneracy (the "seam space") in order to obtain a more general picture of a CI seam. This method, the seam space nudged elastic band (SS-NEB) method, combines the nudged elastic band method with gradient projected MECI optimization. It provides a very efficient way of finding minimum energy seam paths in the conical intersection seam. The method is demonstrated by application to two molecules: ethylene and the green fluorescent protein (GFP) chromophore. The results show that previously known MECIs for these molecules are connected within a single seam, adding further support to previous conjectures that all MECIs are topologically connected in the seam space. Analysis of the nonadiabatic dynamics further suggests that a broad range of seam geometries, not only the vicinity of MECIs, is involved in the nonadiabatic transition events. The current method provides a tool to characterize CI seams in different environments and to explore the importance of the seam in the dynamics.
锥形交叉点(CIs)在光化学反应中起着基础性作用。尽管人们普遍知道锥形交叉点并非孤立点,而是多维的缝,但除了交叉空间内最低能量点(最低能量锥形交叉点或MECIs)紧邻区域之外,探索和表征这些缝的技术却十分匮乏。在此,我们开发了一种方法,通过在保持电子简并性的几何空间(“缝空间”)内的最小能量路径来连接这些MECIs,以便获得更全面的锥形交叉缝图像。这种方法,即缝空间推挤弹性带(SS-NEB)方法,将推挤弹性带方法与梯度投影MECI优化相结合。它提供了一种在锥形交叉缝中寻找最小能量缝路径的非常有效的方式。该方法通过应用于两个分子得以验证:乙烯和绿色荧光蛋白(GFP)发色团。结果表明,这些分子先前已知的MECIs在单个缝内相互连接,进一步支持了先前的推测,即所有MECIs在缝空间中拓扑相连。对非绝热动力学的分析进一步表明,非绝热跃迁事件涉及的缝几何形状范围广泛,不仅包括MECIs附近。当前方法提供了一种工具,用于表征不同环境中的锥形交叉缝,并探索缝在动力学中的重要性。