تقرير
Addressing Strong Correlation by Approximate Coupled-Pair Methods with Active-Space and Full Treatments of Three-Body Clusters
| العنوان: | Addressing Strong Correlation by Approximate Coupled-Pair Methods with Active-Space and Full Treatments of Three-Body Clusters |
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| المؤلفون: | Magoulas, Ilias, Shen, Jun, Piecuch, Piotr |
| سنة النشر: | 2021 |
| المجموعة: | Condensed Matter Physics (Other) |
| مصطلحات موضوعية: | Physics - Chemical Physics, Condensed Matter - Strongly Correlated Electrons, Physics - Computational Physics |
| الوصف: | When the number of strongly correlated electrons becomes larger, the single-reference coupled-cluster (CC) CCSD, CCSDT, etc. hierarchy displays an erratic behavior, while traditional multi-reference approaches may no longer be applicable due to enormous dimensionalities of the underlying model spaces. These difficulties can be alleviated by the approximate coupled-pair (ACP) theories, in which selected $(T_2)^2$ diagrams in the CCSD amplitude equations are removed, but there is no generally accepted and robust way of incorporating connected triply excited ($T_3$) clusters within the ACP framework. It is also not clear if the specific combinations of $(T_2)^2$ diagrams that work well for strongly correlated minimum-basis-set model systems are optimum when larger basis sets are employed. This study explores these topics by considering a few novel ACP schemes with the active-space and full treatments of $T_3$ correlations and schemes that scale selected $(T_2)^2$ diagrams by factors depending on the numbers of occupied and unoccupied orbitals. The performance of the proposed ACP approaches is illustrated by examining the symmetric dissociations of the $\text{H}_6$ and $\text{H}_{10}$ rings using basis sets of the triple- and double-$\zeta$ quality and the $\text{H}_{50}$ linear chain treated with a minimum basis, for which the conventional CCSD and CCSDT methods fail. Comment: 56 pages, 7 tables, 4 figures |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1080/00268976.2022.2057365 |
| URL الوصول: | http://arxiv.org/abs/2111.13787 |
| رقم الأكسشن: | edsarx.2111.13787 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1080/00268976.2022.2057365 |
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