发表机构
Norwegian University of Science and Technology（挪威科技大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
提出一种限制活性空间耦合簇方法，通过仅含双占据到虚轨道的激发算符，对角化相似变换哈密顿量，有效捕获多参考态和开壳层系统的动态相关性。
AI 中文摘要
我们提出了一种用于多参考态和开壳层系统的简单耦合簇方法。在限制活性空间耦合簇框架中，簇算符仅包含从双占据轨道到虚轨道的激发，这确保了各算符之间相互对易。通过在对角化限制活性空间中的耦合簇相似变换哈密顿量，获得基态和激发态。我们针对RAS-CCSD模型展示了该框架，其中簇算符包含单双激发，同样也适用于完全活性空间。我们以自旋适配的方式考虑了具有多参考态特征的系统以及开壳层系统。该方法比没有耦合簇相似变换时捕获了显著更多的动态相关性。
英文摘要
We introduce a simple coupled cluster approach for multireference and open-shell systems. In the restricted active space coupled cluster framework, the cluster operator only includes excitations from doubly occupied to virtual orbitals, and this ensures the individual operators commute among each other. The ground and excited states are obtained by diagonalisation of the coupled cluster similarity transformed Hamiltonian in a restricted active space. We demonstrate the framework for the RAS-CCSD model, where single and double excitations are included in the cluster operator, and likewise for a complete active space. We consider systems with multireference character and open-shell systems in a spin-adapted manner. The approach captures significantly more dynamical correlation than without the coupled cluster similarity transformation.
