Theoretical Methods For Molecular Potential Energy Surfaces and Properties

这个研究项目，其中对待三个具体的计算方法， 在分子电子结构理论中， 理论与计算化学课程。 主题（1）延伸 Pulay现行的无限制自然轨道完全活动空间方法 （UNO-CAS）到大分子（例如具有24个非氢原子的分子） 并且提供了对激发电子态的更精确的描述。 主题（2）有效地包括低阶中的高阶校正 广义Moller Plesset微扰理论 功能 题目（3）采用规范不变的原子轨道， NMR性质的量子力学计算，并探讨了 在密度泛函理论中使用类似的技术。 实验室实验和理论预测，使用计算机模型 基于电子运动的量子力学方程， 今天，作为平等的伙伴， 行为现代分子电子学方法的进展 结构化计算对几乎所有领域都产生了重大影响， 化学从研究地球大气中的小分子到 具有重要生物化学意义的大分子 发展这些 数学方法及其在大型计算机中的实现 这是数百人多年努力的结果。 这个项目 继续这一传统，开发实用，广泛适用， 理论工具。 该项目的目标是提高速度， 分子电子结构计算的准确性，以扩展这些 到更大的分子，处理激发电子态（重要的是 光学性质和某些类别的化学反应），以及 更好地理解分子结构之间的基本关系 并观察核磁共振（NMR）谱。

This research project, which treats three specific computational methods in molecular electronic structure theory, is supported by the NSF Theoretical and Computational Chemistry Program. Topic (1) extends Pulay's current Unrestricted Natural Orbital Complete Active Space method (UNO-CAS) to large molecules (e.g. molecules with 24 nonhydrogen atoms) and provides a more accurate description of excited electronic states. Topic (2) effectively includes higher-order corrections in low-order Generalized Moller Plesset perturbation theory by relaxing the reference function. Topic (3) employs gauge-invariant atomic orbitals for ab initio quantum mechanical calculation of NMR properties, and explores the use of similar techniques in density functional theory. Laboratory experiments and theoretical predictions, using computer models based on the quantum mechanical equations of motion of the electrons, today contribute as equal partners to the understanding of chemical behavior. The evolution of modern methods for molecular electronic structure computation has had a major impact on virtually every field of chemistry from the study of small molecules in the earth's atmosphere to large molecules of biochemical importance. The development of these mathematical methods and their implementation into large scale computer programs is the result of hundreds of man years of effort. This project continues this tradition of developing practical, widely applicable, theoretical tools. The goal of this project is to improve the speed and accuracy of molecular electronic structure computations, to extend these to larger molecules, to treat excited electronic states (important for optical properties and certain classes of chemical reactions), and to better understand fundamental relationships between molecular structure and observed nuclear magnetic resonance (NMR) spectra.