High-level coupled-cluster energetics by Monte Carlo sampling and moment expansions: Further details and comparisons
High-level coupled-cluster energetics by Monte Carlo sampling and moment expansions: Further details and comparisons
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DOI：
10.1063/5.0045468
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发表时间：
2021-03-28
影响因子：
4.4
通讯作者：
Piecuch, Piotr
中科院分区：
文献类型：
--
作者：
Deustua, J. Emiliano;Shen, Jun;Piecuch, Piotr
我们最近提出了一种新的方法，通过将确定性CC（P；Q）形式主义与随机组态相互作用（CI）和CC量子蒙特卡罗（QMC）传播相结合，将电子能量等效于高级耦合簇（CC）计算。本文扩展了我们的初步研究[J]。E. Deustua， J. Shen， P. Piecuch, Phys。Rev. Lett. 119, 223003(2017)]，该研究重点是利用从全CIQMC和CCSDT- mc中提取的信息，将CC方法获得的单双三组（CCSDT）能量恢复到三组和四组截断的CIQMC方法。它还报告了我们的第一个半随机CC（P；Q）计算，旨在将与单、双、三、四组CC方法（CCSDTQ）相对应的能量收敛。半随机CC（P；Q）形式体系恢复CCSDT和CCSDTQ能量的能力，即使当电子准简并和三重和四重激发团簇变得相当大时，通过一些数值例子，包括F-2中的F-F键断裂，环丁二烯的自异构化和水分子的双重解离，来说明。
We recently proposed a novel approach to converging electronic energies equivalent to high-level coupled-cluster (CC) computations by combining the deterministic CC(P;Q) formalism with the stochastic configuration interaction (CI) and CC Quantum Monte Carlo (QMC) propagations. This article extends our initial study [J. E. Deustua, J. Shen, and P. Piecuch, Phys. Rev. Lett. 119, 223003 (2017)], which focused on recovering the energies obtained with the CC method with singles, doubles, and triples (CCSDT) using the information extracted from full CI QMC and CCSDT-MC, to the CIQMC approaches truncated at triples and quadruples. It also reports our first semi-stochastic CC(P;Q) calculations aimed at converging the energies that correspond to the CC method with singles, doubles, triples, and quadruples (CCSDTQ). The ability of the semi-stochastic CC(P;Q) formalism to recover the CCSDT and CCSDTQ energies, even when electronic quasi-degeneracies and triply and quadruply excited clusters become substantial, is illustrated by a few numerical examples, including the F-F bond breaking in F-2, the automerization of cyclobutadiene, and the double dissociation of the water molecule.