Development of Programs for Spin Projection, Energy Derivatives and Advanced Graphics in MO Calculations

该项目由计算科学资助， 理论和计算物理工程倡议 化学课程。 施莱格尔教授的目标是发展技术 用于快速计算化学反应的反应途径， 能垒和键的精确理论预测- 破碎的能量 这项工作，以及施莱格尔教授之前的工作， 有望对实验化学家有很大的用处。 当无限制的Hartree-Fock和Moeller-Plesset扰动 理论用于开壳层体系的反应和键合反应。 解离，来自不需要的自旋状态的污染有时可以被 大到足以严重扭曲能量面 消灭 最大的自旋污染物显著提高了计算的势垒 高度和键离解势。 本项目将 解决所有自旋污染物的湮灭， 自旋投射能量的梯度，自旋湮灭应用于 相关修正、全CI和高阶微扰 理论来检验自旋投影方法。 化学应用于 演示自旋投影方法的实用性将包括 对多重键的自由基加成、自由基抽象的研究 反应、键离解势和双自由基中间体 在环加成反应中。 还将开发新的算法， 自旋投影能量梯度，过渡态优化， 反应路径跟踪，使用分析的基组优化 梯度和IR强度使用电场依赖函数。

This project is being funded under the Computational Science and Engineering Initiative in the Theoretical and Computational Physical Chemistry program. Professor Schlegel's aim is to develop techniques for rapid calculation of reaction pathways for chemical reactions and the accurate theoretical prediction of energy barriers and bond- breaking energies. This work, and prior work by Professor Schlegel, are expected to be of great utility to experimental chemists. When unrestricted Hartree-Fock and Moeller-Plesset perturbation theory are used for reactions of open shell systems and for bond dissociations, contamination from unwanted spin states can sometimes be large enough to distort the energy surface severely. Annihilation of the largest spin contaminant dramatically improves calculated barrier heights and bond dissociation potentials. The present project will address the annihilation of all spin contaminants, calculation of gradients of spin-projected energies, spin annihilation applied to correlation corrections, and full CI and high order perturbation theory to test the spin projected methods. Chemical applications to demonstrate the utility of the spin projected method will include studies of radical additions to multiple bonds, radical abstraction reactions, bond dissociation potentials, and diradical intermediates in cycloaddition reactions. New algorithms will also be developed for gradients of spin projected energies, transition state optimization, reaction path following, basis set optimization using analytical gradients, and IR intensities using electric field-dependent functions.