Author(s) |
Karton, Amir
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Publication Date |
2022-11-17
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Abstract |
<p>It is well established that the basis set convergence of the correlation consistent (cc-pV<i>n</i>Z) basis sets depends on the presence of high-exponent "tight" <i>d</i> functions in the basis set for second-row atoms. The effect has been linked to low-lying <i>3d</i> virtual orbitals approaching the valence shell. However, since most of this effect is captured at the self-consistent field level, the effect of tight <i>d</i> functions in high-level coupled-cluster calculations has not been extensively studied. Here, we construct an extensive data set of 45 second-row species to examine the effect of tight <i>d</i> functions in CCSD, CCSD(T), CCSDT, and CCSDT(Q) calculations in conjunction with basis sets of up to sextuple-ζ quality. The selected set of molecules covers the gamut from systems where the tight <i>d</i> functions play a relatively minor role (e.g., SiH, SH, SiF, PF<sub>3</sub>, HOCl, Cl<sub>2</sub>, and C<sub>2</sub>Cl<sub>2</sub>) to challenging systems containing a central second-row atom bonded to many oxygen or fluorine atoms (e.g., PF<sub>5</sub>, SF<sub>6</sub>, SO<sub>3</sub>, ClO<sub>3</sub>, and HClO<sub>4</sub>) and systems containing many second-row atoms (e.g., P<sub>4</sub>, S<sub>4</sub>, CCl<sub>4</sub>, and C<sub>2</sub>Cl<sub>6</sub>). In conjunction with the cc-pVDZ basis set, we find chemically significant contributions to the total atomization energies (TAEs) of up to ∼2 kcal/mol at the CCSD level, ∼1 kcal/mol at the (T) level, and contributions of up to ∼0.1 kcal/mol for the post-CCSD(T) components. The effects of the tight <i>d</i> functions are diminished with the size of the basis set" however, they are still chemically significant at the CCSD and (T) levels. For example, with the cc-pVTZ basis set, we obtain contributions to the TAEs of up to ∼1.5 and ∼0.3 kcal/mol at the CCSD and (T) levels, respectively, and with the cc-pVQZ basis set, we obtain contributions of up to ∼1.0 and ∼0.2 kcal/mol at the CCSD and (T) levels, respectively. We also find that a simple natural bond orbital population analysis of the <i>3d</i> orbitals of the second-row atom provides a useful <i>a priori</i> indicator of the magnitude of the effect of tight <i>d</i> functions on post-CCSD(T) contribution to the TAEs in oxide and fluoride systems. These results are particularly important in the context of high-level composite ab initio methods capable of confident benchmark accuracy in thermochemical predictions.<p>
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Citation |
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory, 126(45), p. 8544-8555
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ISSN |
1520-5215
1089-5639
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Link | |
Publisher |
American Chemical Society
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Title |
Tightening the Screws: The Importance of Tight d Functions in Coupled-Cluster Calculations up to the CCSDT(Q) Level
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Type of document |
Journal Article
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Entity Type |
Publication
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