Lange Malte F, Berkelbach Timothy C
Department of Chemistry, Columbia University, New York, New York 10027 USA.
Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010 USA.
Mol Phys. 2020;118(19-20). doi: 10.1080/00268976.2020.1808726. Epub 2020 Aug 20.
We evaluate the performance of approaches that combine coupled-cluster and perturbation theory based on a predefined active space of orbitals. Coupled-cluster theory is used to treat excitations that are internal to the active space and perturbation theory is used for all other excitations, which are at least partially external to the active space. We consider a variety of schemes that differ in how the internal and external excitations are coupled. Such approaches are presented for ground states and excited states within the equation-of-motion formalism. Results are given for the ionization potentials and electron affinities of a test set of small molecules and for the correlation energy and band gap of a few periodic solids.
我们基于预先定义的轨道活性空间，评估了结合耦合簇理论和微扰理论的方法的性能。耦合簇理论用于处理活性空间内部的激发，而微扰理论用于处理所有其他激发，这些激发至少部分位于活性空间外部。我们考虑了多种方案，这些方案在内部和外部激发如何耦合方面有所不同。在运动方程形式体系中，针对基态和激发态给出了此类方法。给出了一组小分子测试集的电离势和电子亲和能以及一些周期性固体的相关能和带隙的结果。
