Post-CCSD(T) corrections to bond distances and vibrational frequencies: the power of $Λ$
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arXiv
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| Main Authors: | , , , , |
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| Format: | Preprint |
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2023
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| _version_ | 1866911827758153728 |
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| author | Spiegel, Maciej Semidalas, Emmanouil Martin, Jan M. L. Bentley, Megan R. Stanton, John F. |
| author_facet | Spiegel, Maciej Semidalas, Emmanouil Martin, Jan M. L. Bentley, Megan R. Stanton, John F. |
| contents | The importance of post-CCSD(T) corrections as high as CCSDTQ56 for ground-state spectroscopic constants ($D_e$, $ω_e$, $ω_ex_e$, and $α_e$) 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)$_Λ$ 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)$_Λ$ vs. CCSDTQ5, while CCSDTQ5(6)$_Λ$ is essentially indistinguishable from CCSDTQ56. A composite of CCSD(T)-X2C/ACV5Z-X2C with [CCSDT(Q)$_Λ$ -- 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)$_Λ$ handles them gracefully. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2307_14694 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Post-CCSD(T) corrections to bond distances and vibrational frequencies: the power of $Λ$ Spiegel, Maciej Semidalas, Emmanouil Martin, Jan M. L. Bentley, Megan R. Stanton, John F. Chemical Physics The importance of post-CCSD(T) corrections as high as CCSDTQ56 for ground-state spectroscopic constants ($D_e$, $ω_e$, $ω_ex_e$, and $α_e$) 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)$_Λ$ 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)$_Λ$ vs. CCSDTQ5, while CCSDTQ5(6)$_Λ$ is essentially indistinguishable from CCSDTQ56. A composite of CCSD(T)-X2C/ACV5Z-X2C with [CCSDT(Q)$_Λ$ -- 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)$_Λ$ handles them gracefully. |
| title | Post-CCSD(T) corrections to bond distances and vibrational frequencies: the power of $Λ$ |
| topic | Chemical Physics |
| url | https://arxiv.org/abs/2307.14694 |