Theoretical Studies of Electronic Structure and Dynamical Aspects of Electronically Nonadiabatic Processes

电子非绝热过程的电子结构和动力学方面的理论研究

• 批准号: 9700771
• 负责人: David Yarkony
• 金额: $ 32.55万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-08-01 至 2002-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9700771&HistoricalAwards=false
• 关键词: Theoretical; Studies; Electronic; Structure; Dynamical

The Theoretical and Computational Chemistry Program is supporting Prof. Yarkony at Johns Hopkins University over the next three years. Yarkony's research will focus on fundamental questions concerning the electronic structure aspects of electronically non-adiabatic processes. Of particular interest will be the locus of points of the conical intersection, particularly of two states of the same symmetry. The prevalence and impact of conical intersections will be studied in the ensuing grant period to investigate their role in electronically non-adiabatic processes. A second basic question concerns the diabatic bases routinely used to study the dynamics of non-adiabatic processes. Although routinely used, diabatic bases exist only in an approximate sense. Line integrals of the derivative coupling can be used to determine the size of the nonremovable part of the derivative coupling, that is the portion of the derivative coupling that must remain even in the 'most diabatic' basis. Yarkony will use this technique to identify systems for which the nonremovable part of the derivative coupling is appreciable. For these systems he will use the ab initio derivative couplings to construct the 'most diabatic' basis and compare the results with commonly used but necessarily approximate diabatization procedures. This work is expected to provide fundamental insights to the nature of diabatic bases. The chemistry of molecules exposed to light, photochemistry, is fundamentally different from the chemistry of ground state molecules. The essential difference lies in the interconversion of electronic energy created by the photoexcitation process into vibrational, rotational and translational energy as the molecule relaxes non-adiabatically to the ground electronic state. Although non-adiabatic processes are ubiquitous, occurring for example in vision, photosynthesis, and stratospheric ozone degradation, many basic questions concerning non-adiabatic processes need to be addressed. One of the principal drivers of non-adiabatic processes is a topological feature known as a conical intersection. Once thought to be rare occurrences attributable to special, symmetry, properties of a molecule, it is now clear that like non-adiabatic processes themselves conical intersections are ubiquitous. Yarkony will use a unique system of computer algorithms developed at Johns Hopkins University over the last decade to study fundamental issues related to conical intersections and the way they influence non-adiabatic processes.

理论和计算化学项目将在未来三年内为约翰·霍普金斯大学的 Yarkony 教授提供支持。 亚科尼的研究将集中于有关电子非绝热过程的电子结构方面的基本问题。 特别令人感兴趣的是圆锥形交点的轨迹，特别是相同对称性的两个状态的交点轨迹。 将在随后的资助期内研究圆锥形交叉点的普遍性和影响，以调查它们在电子非绝热过程中的作用。 第二个基本问题涉及通常用于研究非绝热过程动力学的非绝热基。 尽管常规使用，但非绝热基仅以近似意义存在。 导数耦合的线积分可用于确定导数耦合的不可移除部分的大小，即导数耦合的即使在“最非绝热”基础下也必须保留的部分。 Yarkony 将使用该技术来识别导数耦合的不可移除部分明显的系统。 对于这些系统，他将使用从头算导数耦合来构建“最非绝热”基础，并将结果与​​常用但必然近似的非绝热化程序进行比较。 这项工作有望为非绝热基的性质提供基本的见解。 暴露于光下的分子的化学性质（光化学）与基态分子的化学性质根本不同。 本质区别在于，当分子非绝热弛豫到电子基态时，光激发过程产生的电子能相互转换为振动能、旋转能和平移能。 尽管非绝热过程无处不在，例如发生在视觉、光合作用和平流层臭氧降解中，但有关非绝热过程的许多基本问题需要解决。 非绝热过程的主要驱动因素之一是称为圆锥形交叉的拓扑特征。 曾经被认为是由于分子的特殊、对称性和性质而罕见的现象，现在很明显，就像非绝热过程本身一样，圆锥形相交是普遍存在的。 Yarkony 将使用约翰·霍普金斯大学在过去十年中开发的独特计算机算法系统来研究与圆锥相交相关的基本问题及其影响非绝热过程的方式。