CDS&E: Advances in Coupled-Cluster Theory with Molecular Applications

得克萨斯大学奥斯汀分校的约翰·斯坦顿获得了化学部化学理论、模型和计算方法计划以及计算和数据科学与工程计划(CDS&amp；E)的支持，该计划旨在开发理论方法和软件来描述电子被激发的分子的性质。这项工作的主要目的是开发和使用量子力学方法来理解分子光谱学领域的实验并预测结果。光谱学研究分子如何与电磁辐射相互作用。通过研究特定分子在不同波长(能量)辐射下的行为，可以确定分子的结构，并推断控制分子的化学反应和其他行为的大部分详细信息。该项目的一个主要目标是开发有助于分析分子在可见光和紫外线能量范围内的光谱的量子力学方法，这是驱动化学的电子最相关的区域。斯坦顿小组开发的计算方法和工具包含在一个免费的公开可用的计算机程序CFOUR中，该程序计算出非常精确的量，可以与实验进行比较。这一计算机代码利用了最先进的计算机体系结构。研究生和本科生都参与了这些项目。这项工作涉及包括星际和大气化学在内的许多领域。在传统量子化学方面，斯坦顿和他的研究小组专注于在非常高水平的耦合团簇理论中开发方法，特别是那些涉及四重激发效应的方法。这包括能量和梯度计算的方法，以及可以通过运动方程方法获得的自由基、离子和激发态的扩展。所有的方法都被合并到CFOUR程序包中，从而产生了新的程序模块，这些模块将利用大规模并行计算机提供的优势。其他研究集中在光谱学中的非绝热效应，既在解释工具的开发中，也在程序的开发中。虽然计算机程序开发是计划研究的主要重点，但上述对解释工具的调查本质上不是计算性的。在他的方面类似的是另外两个项目活动：建立和基准工具，用于分析处理特定问题的特定水平的耦合-集群理论的充分性；以及分析米勒的半经典过渡态理论的一些形式性质。

John Stanton of the University of Texas at Austin is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division and the Computational and Data-Enabled Science and Engineering program (CDS&E) to develop theoretical methods and software to describe the properties of molecules in which the electrons have been excited. The major thrust of the work is to develop and use quantum mechanical methods to understand experiments in the field of molecular spectroscopy and to predict the results. Spectroscopy probes how molecules interact with electromagnetic radiation. By investigating how a particular molecule behaves at various wavelengths (energies) of irradiation, one can determine the structure of the molecule as well as infer most of the detailed information that governs the chemical reactivity and other behavior of the molecule. A major goal of the project is to develop quantum-mechanical methods that are useful for analyzing the spectra of molecules in the visible and ultraviolet energy ranges, which is the most relevant region for the electrons that drive chemistry. The computational methods and tools developed by the Stanton group are embodied in a free and publicly available computer program, CFOUR, which computes very accurate quantities that can be compared with experiment. This computer code takes advantage of state-of-the-art computer architecture. Both graduate and undergraduate students are involved in these projects. The work has relevance to many fields including interstellar and atmospheric chemistry.In terms of traditional quantum chemistry, Stanton and his research group focus on methods development at very high levels of coupled-cluster theory, specifically those that involve quadruple excitation effects. This includes methods for energy and gradient calculations, as well as extension to radicals, ions and excited states that can be accessed by the equation-of-motion approach. All methods are incorporated into the CFOUR program package, leading to new program modules that will exploit advantages offered by massively parallel computers. Additional research focuses on non-adiabatic effects in spectroscopy, both in the development of interpretive tools as well as development of programs. While computer program development is a major focus of the planned research, the aforementioned investigation of interpretive tools is not computational in nature. Similar in his respect are two other project activities: the establishment and benchmarking of a tool for analyzing the adequacy of particular levels of coupled-cluster theory for treating specific problems; and analysis of some formal properties of Miller's semiclassical transition state theory.