International Research Fellowship Program: Chemical Reactions Involving Multiple Electronic States

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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.