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

德克萨斯大学奥斯汀分校的约翰·斯坦顿（John Stanton）获得了化学学部化学理论、模型和计算方法项目以及计算和数据支持科学与工程项目（CDS&amp；E）的奖励，以开发理论方法和软件来描述电子被激发的分子特性。工作的主要推力是发展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）照射下的行为，人们可以确定分子的结构，并推断出控制分子化学反应性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量子力学方法，用于分析可见和紫外线能量范围内的分子光谱，这是与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且公开的计算机程序CFOUR中，它可以计算出与实验相比较的非常精确的数量。这个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。这项工作涉及许多领域，包括星际化学和大气化学。在传统的量子化学方面，Stanton和他的研究小组专注于高水平耦合簇理论的方法开发，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方法，以及扩展到可以通过运动方程方法访问的自由基，离子和激发态。所有的方法都被整合到CFOUR程序包中，导致新的程序模块将利用大规模并行计算机提供的优势。另外的研究重点是非绝热效应在光谱学，无论是在解释工具的发展和发展的程序。虽然计算机程序开发是计划研究的主要焦点，但上述解释工具的调查本质上不是计算性的。与他的观点类似的还有另外两项项目活动：建立一种工具并对其进行基准测试，以分析处理具体问题的耦合聚类理论的特定层次是否足够；并分析了米勒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.