Development and Applications of Electronic Structure Methods for Open-shell and Electronically Excited Species with Strongly Interacting States of Different Character

南加州大学的安娜Krylov得到理论和计算化学计划的支持，为开壳层和电子激发物种开发电子结构方法，特别是那些具有不同性质的强相互作用电子态的物种。该计划利用PI最近在开发新的运动方程（EOM）耦合簇（CC）方法方面的进展，该方法扩展了这种强大而有效的技术来治疗双自由基，三自由基和键断裂。计划进行以下方法发展：（一）探索Fock空间的更高部分（例如，双自旋翻转、自旋翻转（双）电离等）扩展EOM的情况下，遇到多个键断裂，在过渡金属和多自由基更广泛的简并;（ii）包括更高的激发，以实现化学精度;（iii）自旋自适应的开壳CC和EOM波函数，以提高在有问题的情况下，如自旋污染或不稳定的参考精度。新方法将用于研究燃烧和大气化学中涉及的开壳层物种的电子结构以及实际相关的自由基阴离子反应（即，苯炔和富烯阴离子），继续与实验小组合作。这项研究预计将导致对环境和技术重要性问题的新见解，例如与大气和合成化学有关的化学反应系统。 这项研究还包括计算机代码设计和实现的一个重要组成部分，并将帮助学生为高科技行业的职业生涯做好准备，这些行业高度重视使用复杂计算工具解决复杂问题的能力。 新的计算机软件将被整合到广泛使用的电子结构程序中，使这些结果可供广大的化学界使用。

Anna Krylov of the University of Southern California is supported by the Theoretical and Computational Chemistry Program to develop electronic structure methodology for open-shell and electronically excited species, in particular for those with strongly interacting electronic states of different nature. The proposed program capitalizes on the PI's recent advances in developing new equation-of-motion (EOM) coupled-cluster (CC) methods, which extend this robust and efficient technique to treat diradicals, triradicals, and bond-breaking. The following methodological developments are planned: (i) exploring higher sectors of the Fock space (e.g., double spin-flip, spin-flip - (double) ionization, etc.) to extend EOM to situations with more extensive degeneracies encountered upon multiple bond-breaking, in transition metals and polyradicals; (ii) including higher excitations to achieve chemical accuracy; (iii) spin-adaptation of open-shell CC and EOM wave functions to improve accuracy in problematic cases such as spin-contaminated or unstable references. The new methodology will be applied to study electronic structure of open-shell species involved in combustion and atmospheric chemistry as well as practically relevant radical anionic reactions (i.e., benzyne and fulvene anions), in continuing collaborations with experimental groups. This research is expected to lead to new insights into problems of environmental and technological importance, for example chemical reaction systems that are relevant to atmospheric and synthetic chemistry. This research also includes a strong component of computer code design and implementation, and will help prepare students for careers in high-tech industries where the ability to solve complex problems using sophisticated computational tools is highly valued. New computer software will be integrated into widely available electronic structure programs, making these results available to the broad chemistry community.