Waigum A, Black J A, Köhn A
Institut für Theoretische Chemie, Universität Stuttgart, Pfaffenwaldring 55, D-70569 Stuttgart, Germany.
J Chem Phys. 2021 Nov 28;155(20):204106. doi: 10.1063/5.0067511.
A generalization of the hybrid scheme for multireference methods as recently put forward by Saitow and Yanai [J. Chem. Phys. 152, 114 111 (2020)] is presented. The hybrid methods are constructed by defining internal and external excitation spaces and evaluating these two subsets of excitations at different levels of theory. New hybrids that use the mix of internally contracted multireference coupled-cluster, unshifted multireference coupled electron pair, and multireference perturbation methods are derived and benchmarked. A new separation of the excitation space, which combines all singles and doubles excitations to the virtual orbitals into the external space, is also presented and tested. In general, the hybrid methods improve upon their non-hybrid parent method and offer a good compromise between computational complexity and numerical accuracy.
本文提出了对Saitow和Yanai [《化学物理杂志》152, 114 111 (2020)] 最近提出的多参考方法混合方案的一种推广。通过定义内部和外部激发空间，并在不同理论水平上评估这两个激发子集来构建混合方法。推导并测试了使用内部收缩多参考耦合簇、未移位多参考耦合电子对和多参考微扰方法混合的新混合方法。还提出并测试了一种新的激发空间分离方法，该方法将所有单重和双重激发到虚拟轨道的激发合并到外部空间。一般来说，混合方法比其非混合母方法有所改进，并在计算复杂度和数值精度之间提供了良好的折衷。
