Theoretical Methods for Molecular Potential Surfaces

本项目属于理论与计算化学专业，主要研究分子电子结构计算的几种改进方法。解析能量梯度方法将在局部相关方法中实现，以方便大分子基态的几何确定。在初步计算超高频自然轨道的基础上，提出了一种无偏选择有源MCSCF轨道的新方法，并将其推广到激发态。本文将实现并测试一种新的微扰理论，用于确定开壳态和多参考态的相关能。基于超高频态的类似微扰理论也将通过消除自旋污染的新方法得到改进。总的来说，这些发展将极大地扩展化学问题的范围，这些问题可以通过精确的计算方法来解决。

This project in the Theoretical and Computational Chemistry program concerns the development of several improved methods for carrying out electronic structure calculations on molecules. Analytic energy gradient methods will be implemented in the Local Correlation Method to facilitate geometry determinations of the ground states of large molecules. A new method for unbiased selection of active MCSCF orbitals, based on preliminary calculation of UHF natural orbitals, will be generalized to excited states. A new perturbation theory for determination of correlation energies in open shell and multi-reference states will be implemented and tested. The analogous perturbation theory based on UHF states will also be improved by a new method of eliminating spin contamination. Taken together, these developments will greatly extend the range of chemical problems that can be addressed by accurate computational methods.