New Developments in Coupled Cluster Theory and Applications

在化学系理论与计算项目的资助下，Scuseria教授将开发新的算法，将耦合簇摄动理论应用于分子电子结构的研究。这一理论将有助于理解过渡金属二聚体、氢化物和乙炔的碳氢键的化学键。将进行四项研究项目。(1)开壳耦合簇法中解析能量梯度容量的建立与实现。(2)实现了包括单、双、三重和四重激励的全耦合簇方法。(3)耦合簇方程的一种解，它试图将三重激励的影响直接转移到单激励和双激励的振幅上。(4)基于Hartree-Fock-Bogoliubov参考状态的耦合簇理论公式，作为传统多参考方法的替代方案。

With this grant in the Theoretical and Computational Program of the Chemistry Division, Professor Scuseria will develop new algorithms for the application of coupled-cluster perturbation theory to the study of molecular electronic structure. This theory will be instrumental in understanding chemical bonding in transition metal dimers, hydrides and the C-H bond of acetylene. Four research projects will be carried out. (1) The formulation and implementation of an analytical energy gradient capacity within the open shell coupled-cluster method. (2) The implementation of a full coupled-cluster method that includes all single, double, triple and quadruple excitations. (3) A solution of the coupled-cluster equations that attempts to transfer the effect of triple excitations directly onto the single and double excitation amplitudes. (4) A formulation of the coupled-cluster theory in terms of the Hartree-Fock-Bogoliubov reference state as an alternate to the conventional multi-reference approach.