Advances in Coupled-Cluster Theory with Molecular Applications

佛罗里达大学的John Stanton得到了化学系化学理论、模型和计算方法项目的支持。 斯坦顿和他的研究小组在理论化学物理领域工作，旨在将物理学的概念应用于原子和分子的研究。 他们在两个研究领域工作：量子化学和分子动力学。 在量子化学中，斯坦顿小组开发并应用了一类用于处理电子的方法的计算工具，称为耦合簇理论，以实现对实验人员感兴趣的分子性质的高度精确计算。 在分子动力学中，他们开发了半经典过渡态理论的方法，使预测和理解化学反应发生的速率成为可能。 量子化学研究的潜在应用包括 非常详细的计算，以提高化学模型的保真度，研究大气和工业中的化学过程。 通过将量子化学的工作与反应速率理论的发展相结合，他们可以对涉及自由基和双自由基的化学反应进行精确的研究。后一个研究领域在许多领域都有重要意义，因为对生命如此重要的氧分子，占大气的20%，是一种双自由基。 在这项研究中开发的量子化学方法都在CFOUR量子化学包中实现，该包可免费提供给研究社区。 斯坦顿正在他的大学里为学习自然科学的高积极性和高成就的学生开发一个荣誉项目。拟议的研究涉及电子相关的耦合簇处理的探索，特别是涉及高精度的方法，包括四重激励的影响和多参考效应，这是无处不在的特征。（和重要的）一类问题，包括“biradical”系统。 此外，我们还将努力探索半经典过渡态理论的准确性和局限性，包括：对多维模型系统的精确量子结果进行基准测试，设计该方法的扩展，并探索该方法处理的伪态与Siegert本征态之间的正式联系。 此外，还将开展工作，开发包括角动量效应在内的分子中电子振动耦合的治疗方法，最终设计和实施自旋-旋转电子振动治疗。

John Stanton of the University of Florida is supported by an award from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry. Stanton and his research group work in the field of theoretical chemical physics, which aims to apply concepts from physics to the study of atoms and molecules. They work in two research areas: quantum chemistry and molecular dynamics. In quantum chemistry, the Stanton group develops and applies computational tools from the class of methods for treating electrons that is known as coupled-cluster theory to enable highly accurate calculations of the properties of molecules that are of interest to experimentalists. In molecular dynamics, they develop approaches to semiclassical transition state theory, enabling the prediction and understanding of the rates at which chemical reactions take place. Potential applications of the quantum chemistry research include very detailed calculations to improve the fidelity of chemical models to study chemical processes in the atmosphere and industry. By combining the work in quantum chemistry with the reaction rate theory developments, they can perform accurate studies of chemical reactions involving radicals and biradicals. This latter area of research has significant import in many areas, since the oxygen molecule so vital to life and which constitutes 20% of the atmosphere is a biradical. The quantum chemistry methods that are developed in this research are all implemented in the CFOUR quantum chemistry package, which is freely available to the research community. Stanton is working to develop an honors program at his university for highly-motivated and highly-accomplished students enrolled in the study of the natural sciences.The proposed research involves explorations in the coupled-cluster treatment of electronic correlation, specifically involving high-accuracy methods including effects of quadruple excitations and the multireference effects that are characteristic of the ubiquitous (and important) class of problems that comprise "biradical" systems. In addition, work will be done to explore the accuracy and limits of semiclassical transition state theory, involving: benchmarking against exact quantum results for multidimensional model systems, designing extensions of the method, and exploring the formal connections between the pseudo-states treated by this method and Siegert eigenstates. In addition, work will be done on developing methods for the treatment of vibronic coupling in molecules that include angular momentum effects, culminating in the design and implementation of a spin-rovibronic treatment.