Post-CCSD(T) corrections to bond distances and vibrational frequencies: the power of Λ

被引：7
|
作者：
Spiegel M. [1 ,2 ]
Semidalas E. [1 ]
Martin J.M.L. [1 ]
Bentley M.R. [3 ]
Stanton J.F. [3 ]
机构：
[1] Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Reovot
[2] Department of Pharmacognosy and Herbal Medicines, Wroclaw Medical University, Wrocław
[3] Quantum Theory Project, Department of Chemistry, University of Florida, Gainesville, FL
来源：
Molecular Physics | 2024年 / 122卷 / 7-8期
基金：
以色列科学基金会;
关键词：
Coupled cluster theory; diatomic molecules; lambda coupled cluster; ozone; vibrational frequencies;
D O I：
10.1080/00268976.2023.2252114
中图分类号：
学科分类号：
摘要：
The importance of post-CCSD(T) corrections as high as CCSDTQ56 for ground-state spectroscopic constants ((Formula presented.), (Formula presented.), (Formula presented.), and (Formula presented.)) has been surveyed for a sample of two dozen mostly heavy-atom diatomics spanning a broad range of static correlation strength. While CCSD(T) is known to be an unusually felicitous ‘Pauling point’ between accuracy and computational cost, performance leaves something to be desired for molecules with strong static correlation. We find CCSDT(Q) (Formula presented.) to be the next ‘sweet spot’ up, of comparable or superior quality to the much more expensive CCSDTQ. A similar comparison applies to CCSDTQ(5) (Formula presented.) vs. CCSDTQ5, while CCSDTQ5(6) (Formula presented.) is essentially indistinguishable from CCSDTQ56. A composite of CCSD(T)-X2C/ACV5Z-X2C with [CCSDT(Q) (Formula presented.)–CCSD(T)]/cc-pVTZ or even cc-pVDZ basis sets appears highly effective for computational vibrational spectroscopy. Unlike CCSDT(Q) which breaks down for the ozone vibrational frequencies, CCSDT(Q) (Formula presented.) handles them gracefully. © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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