Metastable electronic states: electronic structure, dynamics, and chemistry

电子-分子相互作用通常会导致复杂的化学反应，该化学反应由电子捕获引发，进入一种临时状态，该状态具有足够的能量来发射电子，但寿命足够长，足以引发化学反应。因此，这种亚稳态的寿命决定了化学转化的时间尺度。亚稳电子态是生物分子辐射损伤的关键中间体，并且它们也通常在高能环境（例如等离子体）中形成。该研究计划提出了新模型的发展，使亚稳态电子态的能量和寿命的定量预测。所概述的计算研究旨在促进对亚稳态在生物系统的辐射损伤、光化学和催化中的作用的理解，所提出的研究目标有三个方面：（i）实现Feshbach和多激发共振的鲁棒关联处理;（ii）通过Born-Oppenheimer从头算动力学模型纳入核运动;（iii）将核运动与核动力学模型结合起来。（iii）将共振的电子结构方法与描述金属表面化学反应的密度泛函嵌入方法相结合。所提出的方法将适用于现实的分子系统（~ 50-100个原子）。具体地说，提出了一种新的方法相结合的复吸收势的方法和扩展的多组态准生微扰理论，使Feshbach和多重激发共振的位置和宽度的计算。由于通过电子发射和核弛豫的共振衰减通常发生在同一时间尺度上，因此考虑核运动对于理解电子-分子相互作用至关重要。复杂势能面上的Born-Oppenheimer从头算动力学将以动态方式实现，以描述相互依赖的电子喷射和核运动。该模型的简单性使其适用于大分子系统。最后，提出了一种混合的方法相结合的电子结构方法与密度嵌入技术的共振占亚稳态的金属表面上的反应所涉及的临时状态。一个特别的重点是执行开发的方法，作为有效的代码，可通过广泛使用的软件包和开放源码模块，通过PI的网站。外展计划包括由PI在波士顿大学为高中暑期研究生举办的年度计算化学研讨会。

Electron-molecule interactions often lead to complex chemistry initiated by electron capture into a temporary state that has enough energy to eject an electron, yet, lives long enough to trigger a chemical reaction. The lifetime of this metastable state, therefore, sets the timescale for the chemical conversion. Metastable electronic states are key intermediates in radiation damage of biomolecules and they are also routinely formed in highly energetic environments, e.g. plasmas. This research program proposes development of new models enabling quantitative predictions of the energies and lifetimes of metastable electronic states. The outlined computational studies are aimed at advancing the understanding of the role of metastable states in radiation damage of biological systems, in photovoltaics, and catalysis.The goals of the proposed research are three-fold: (i) enabling robust correlated treatment of Feshbach and multiply-excited resonances; (ii) incorporating nuclear motion via Born-Oppenheimer ab initio dynamics models; (iii) integrating electronic structure methods for resonances with density functional embedding approaches for the description of chemical reactions on metal surfaces. The proposed methods will be applicable to realistic molecular systems (~ 50-100 atoms). Specifically, a new method combining the complex absorbing potential approach and extended multiconfigurational quasidegenerate perturbation theory is proposed to enable calculations of Feshbach and multiply-excited resonances' position and widths. Since resonance decay via electron ejection and nuclear relaxation often occur on the same timescale, taking into account nuclear motion is crucial for understanding electron-molecular interactions. Born-Oppenheimer ab initio dynamics on complex potential energy surfaces will be implemented in the on-the-fly manner to describe interdependent electron ejection and nuclear motion. The simplicity of the model makes it applicable to large molecular systems. Finally, a hybrid approach combining electronic structure methods for resonances with density embedding techniques is proposed to account for the metastable character of temporary states involved in reactions on metal surfaces. A special emphasis is placed on implementing the developed methodologies as efficient codes available through widely used software packages and as open-source modules via the PI's website. The outreach program includes an annual computational chemistry workshop for high-school summer research students hosted by PI at Boston University.