Theoretical Methods for Molecular Potential Surfaces

这个理论与计算化学的项目 该计划涉及几种改进方法的发展 进行电子结构计算 分子。 分析能量梯度方法将是 在局部相关方法中实现，以便于 大分子基态的几何确定 分子。 主动MCSCF无偏选择的一种新方法 轨道，根据初步计算的UHF自然 轨道，将被推广到激发态。 一个新 微扰理论测定关联能 在开壳和多引用状态下， 和测试。 基于超高频的类微扰理论 国家也将通过一种新的方法来改善消除 自旋污染 综合起来，这些发展将 大大扩展了化学问题的范围， 通过精确的计算方法解决。

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.