International Research Fellowship Program: Chemical Reactions Involving Multiple Electronic States

[401585 . netzloff]国际研究奖学金计划使美国科学家和工程师能够在国外进行三到二十四个月的研究。该计划的奖励为联合研究提供了机会，并利用独特或互补的设施、专业知识和国外的实验条件。该奖项将支持Heather M. Netzloff博士与Michael a. Collins博士在澳大利亚堪培拉的澳大利亚国立大学进行为期22个月的研究。本项目旨在开发方法和程序来研究在多电子状态下由分子动力学发生的化学反应。许多化学反应是在分子处于基电子态时发生的。原子的运动受单个分子势能面（PES）的支配。然而，许多重要的化学反应，从大气化学到有机和无机化学中的光化学反应机制，再到光合作用等基本生物现象，都是通过不止一种电子态的动力学进行的。在过去的几年中，Michael Collins博士及其同事开发了一种自动化方法来构建单个PES，然后在一个名为GROW的程序包中研究PES上的反应动力学。最近，Collins博士、Mark Gordon博士和受奖人合作，实现了GROW与从头算量子化学项目GAMESS的部分对接。在此接口之前，当激发态接近基态时，GROW无法构建PES。能量接近的多个电子态只能通过所谓的多参考方法，特别是多构型自洽场（MCSCF）方法来可靠地计算。MCSCF波函数的高效计算是GAMESS的标志能力之一。这个博士后奖学金使极大地扩展GAMESS-GROW界面的能力成为可能，为研究激发态和多电子态的化学反应提供了手段。在grow - gamess接口中包含MCSCF计算使得生长多引用PESs成为可能。就其本身而言，这开辟了广泛的新的重要应用。该项目的第一个重要成果将是推导和编码所谓的“导数耦合”的有效评估，将核运动与电子波函数耦合到GAMESS中。这将首先在MCSCF波函数中完成，然后在更高的理论水平上完成。一个有效的GAMESS-GROW界面将为有效地构建控制化学反应的全局多个PESs和耦合表面提供手段。这些工具的应用将允许研究重要的自由基反应的动力学，以前不能用从头算表面来研究。最初的重点将放在OH和CH自由基的反应上，它们在燃烧化学、地球和其他行星大气化学以及星际化学中起着重要作用。

0401585NetzloffThe International Research Fellowship Program enables U.S. scientists and engineers to conduct three to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.This award will support a twenty-two-month research fellowship by Dr. Heather M. Netzloff to work with Dr. Michael A. Collins at Australian National University in Canberra, Australia.This project aims to develop methods and programs to study chemical reactions that occur by molecular dynamics in multiple electronic states. Many chemical reactions occur while the molecule remains in the ground electronic state. The motion of the atoms is governed by a single molecular potential energy surface (PES). However, many important chemical reactions, ranging from atmospheric chemistry to photochemical reaction mechanisms in organic and inorganic chemistry to fundamental biological phenomena such as photosynthesis, take place via dynamics on more than one electronic state. Over the last several years, Dr. Michael Collins and co-workers have developed an automated method to construct a single PES and to then study the dynamics of reactions on the PES in a program package called GROW. A recent collaboration involving Dr. Collins, Dr. Mark Gordon, and the recipient, resulted in the partial interface of GROW with the ab initio quantum chemistry program, GAMESS. Before this interface, GROW was not capable of constructing a PES when excited electronic states are close to the ground state. Multiple electronic states, close in energy, can only be reliably calculated by using so-called multi-reference methods, in particular multi-configuration self consistent field (MCSCF) approaches. The efficient computation of MCSCF wavefunctions is one of GAMESS' hallmark capabilities. This postdoctoral fellowship is making it possible to enormously expand the power of the GAMESS-GROW interface to provide the means to study chemical reactions in excited electronic states and reactions which proceed via multiple electronic states. The inclusion of MCSCF calculations within the Grow-GAMESS interface makes it possible to grow multi-reference PESs. By itself, this opens up a wide range of new, important applicationsThe first important outcome of the project will be the derivation and coding of the efficient evaluation of the so-called "derivative coupling" that couples nuclear motion with the electronic wavefunction into GAMESS. This will initially be accomplished for MCSCF wavefunctions and subsequently at higher levels of theory. An effective GAMESS-GROW interface will provide the means for efficiently constructing the global multiple PESs and coupling surfaces that govern chemical reactions. Application of these tools will allow the study of the dynamics of important radical reactions that previously could not be studied with ab initio surfaces. The initial focus will be on the reactions of OH and CH radicals, which play important roles in combustion chemistry, in the chemistry of Earth's and other planetary atmospheres, and in interstellar chemistry.