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

德克萨斯大学奥斯汀分校的John Stanton获得了化学系化学理论，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 E）的支持，以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。光谱学探测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，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，用于分析可见光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体现在一个免费和公开的计算机程序CFOUR中，该程序计算出可以与实验进行比较的非常精确的量。 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。 在传统的量子化学方面，Stanton和他的研究小组专注于在非常高水平的耦合团簇理论，特别是那些涉及四重激发效应的方法开发。 这包括用于能量和梯度计算的方法，以及可以通过运动方程方法访问的自由基、离子和激发态的扩展。所有方法都被纳入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。 其他的研究集中在光谱学中的非绝热效应，包括解释工具的开发和程序的开发。虽然计算机程序开发是计划研究的主要重点，但上述解释工具的调查本质上不是计算性的。 他的另两个项目活动也是类似的：建立一个工具，并对该工具进行基准测试，以分析耦合簇理论在处理特定问题时的特定水平的充分性;分析米勒的半经典过渡态理论的一些形式属性。

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.