RUI: Development of Computational Methods and Applications to Molecules in Microsolvation Environments.

RUI：微溶剂化环境中分子的计算方法和应用的开发。

• 批准号: 1565495
• 负责人: Thomas Sommerfeld
• 金额: $ 10.18万
• 依托单位: Southeastern Louisiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1565495&HistoricalAwards=false
• 关键词: RUI; Development; Computational; Methods; Applications

Thomas Sommerfeld of Southeastern Louisiana University is supported by an award from the Chemical Theory, Models and Computational Method program in the Chemistry Division and the NSF EPSCoR office to investigate how extra electrons aid in breaking chemical bonds. Chemical bonds themselves are electrons shared between atoms and can be thought of as a glue holding the atoms in a molecule together. The electron-glue analogy, however, only goes so far, because a bond can be weakened by both too little and too much glue, and weak bonds can be cleaved during the permanent motion of the atoms. In other words, adding an electron to a molecule generally weakens its bonds, and the resulting so-called temporary anion may undergo either bond cleavage or, alternatively, reemit the extra electron. Concrete examples where this reaction is applied or happens naturally are: plasma chemistry and plasma etching, chemistry in the ionosphere, damage to living tissue by ionizing radiation, cancer therapy with electron beams, and reduction reactions with solvated electrons, the so-called Birch reduction. This research project supports the development of computer models of the temporary anion, the first intermediate formed in these electron-induced reactions. This research is carried out with collaborators and with undergraduate researchers. In order to introduce undergraduates to this research, Dr. Sommerfeld also designs educational mini-projects, which are only indirectly related to the current main project, but can be addressed with standard quantum chemistry methods, so that his students can be introduced to the research area step-by-step. In this project Dr. Sommerfeld studies electronically metastable states - so called resonance states or, simply, resonances. On the one hand, he develops ab initio methods to characterize resonances, and on the other hand he applies the newly developed methods in selected applications. Computing both the energy and finite lifetime of a resonance is still a notoriously challenging task for quantum chemistry, because it combines an electron-scattering with an electron-correlation problem. To address the continuum aspect, Dr. Sommerfeld either uses complex-absorbing-potentials or the analytic-continuation-in-the-coupling-constant method. To address the correlation aspect, he uses the symmetry-adapted-cluster configuration-interaction method, an electronic structure method closely related to the equation-of-motion coupled-cluster method. One particular point of emphasis is the artificial stabilizing potential added to the Hamiltonian in the analytic-continuation-in-the-coupling-constant method. Dr. Sommerfeld aims to identify a short-range stabilizing potential that improves the subsequent analytic-continuation step. On the application side Dr. Sommerfeld's goals are to examine resonance states, which differ in electronic structure from a closed-shell neutral either by one-hole (Auger-like resonances) or by one excitation (e.g. Penning ionization or resonant photodetachment). For these resonances, treating electron correlation in a balanced way is particularly challenging. Dr. Sommerfeld studies temporary anion resonances embedded in small molecule clusters with the goal of identifying trends in the change of the resonance parameters associated with the interaction strength (permanent dipole, higher order multipoles, dispersion) of the embedding molecules.

东南路易斯安那大学的托马斯·索默菲尔德 (Thomas Sommerfeld) 获得了化学部化学理论、模型和计算方法项目以及 NSF EPSCoR 办公室的资助，以研究额外的电子如何帮助破坏化学键。化学键本身是原子之间共享的电子，可以被视为将分子中的原子粘合在一起的胶水。然而，电子胶的类比只能到此为止，因为胶水太少和太多都会削弱键，而弱键可能会在原子的永久运动过程中断裂。换句话说，向分子添加电子通常会削弱其键，并且产生的所谓临时阴离子可能会发生键断裂，或者重新发射额外的电子。应用或自然发生该反应的具体例子有：等离子体化学和等离子体蚀刻、电离层中的化学、电离辐射对活体组织的损害、电子束的癌症治疗以及溶剂化电子的还原反应，即所谓的桦木还原。 该研究项目支持临时阴离子计算机模型的开发，临时阴离子是这些电子诱导反应中形成的第一个中间体。 这项研究是与合作者和本科研究人员一起进行的。 为了向本科生介绍这项研究，索末菲博士还设计了教育迷你项目，这些项目仅与当前的主要项目间接相关，但可以用标准的量子化学方法来解决，以便他的学生能够了解这项研究区域逐步。在这个项目中，索末菲博士研究电子亚稳态——所谓的共振态，或者简称共振。一方面，他开发了从头开始的方法来表征共振，另一方面，他将新开发的方法应用于选定的应用中。计算共振的能量和有限寿命对于量子化学来说仍然是一项众所周知的挑战性任务，因为它结合了电子散射和电子相关问题。为了解决连续统方面的问题，索末菲博士要么使用复数吸收势法，要么使用耦合常数解析连续法。 为了解决相关性问题，他使用了对称适应团簇构型相互作用方法，这是一种与运动方程耦合团簇方法密切相关的电子结构方法。一个特别强调的点是在耦合常数解析连续方法中添加到哈密顿量的人工稳定势。索末菲博士的目标是确定一种短程稳定电位，以改进后续的分析延续步骤。在应用方面，索末菲博士的目标是检查共振态，共振态的电子结构与闭壳中性态不同，要么通过单孔（俄歇共振），要么通过一次激发（例如潘宁电离或共振光分离）。对于这些共振，以平衡的方式处理电子相关性尤其具有挑战性。 索末菲博士研究嵌入小分子簇中的临时阴离子共振，目的是确定与嵌入分子相互作用强度（永久偶极子、高阶多极子、色散）相关的共振参数变化趋势。