The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods

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Article discussing research on the correlation consistent composite approach (ccCA) and an alternative to the Gaussian-n methods.

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17 p.

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DeYonker, Nathan J.; Cundari, Thomas R., 1964- & Wilson, Angela K. March 17, 2006.

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Article discussing research on the correlation consistent composite approach (ccCA) and an alternative to the Gaussian-n methods.

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17 p.

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Copyright 2006 American Institute of Physics. J. Chem. Phys. 124, 114104 (2006); http://dx.doi.org/10.1063/1.2173988

Abstract: An alternative to the Gaussian-n (G1, G2, and G3) composite methods of computing molecular energies is proposed and is named the "correlation consistent composite approach" (ccCA, ccCA-CBS-1, ccCA-CBS-2). This approach uses the correlation consistent polarized valence (cc-pVXZ) basis sets. The G2-1 test set of 48 enthalpies of formation (∆Hf), 38 adiabatic ionization potentials (IPs), 25 adiabatic electron affinities (EAs), and 8 adiabatic proton affinities (PAs) are computed using this approach, as well as the ∆Hf values of 30 more systems. Equilibrium molecular geometries and vibrational frequencies are obtained using B3LYP density functional theory. When applying the ccCA-CBS method with the cc-pVXZ series of basis sets augmented with diffuse functions, mean absolute deviations within the G2-1 test set compared to experiment are 1.33 kcal molˉ¹ for ∆Hf, 0.81 kcal molˉ¹ for IPs, 1.02 kcal molˉ¹ for EAs, and 1.51 kcal molˉ¹ for PAs, without including the "high-level correction" (HLC) contained in the original Gn methods. Whereas the HLC originated in the Gaussian-1 method as an isogyric correction, it evolved into a fitted parameter that minimized the error of the composite methods, eliminating its physical meaning. Recomputing the G1 and G3 enthalpies of formation without the HLC reveals a systematic trend where most ∆Hf values are significantly higher than experimental values. By extrapolating electronic energies to the complete basis set (CBS) limit and adding G3-like corrections for the core-valence and infinite-order electron correlation effects, ccCA-CBS-2 often underestimates the experimental ∆Hf, especially for larger systems. This is desired as inclusion of relativistic and atomic spin-orbit effects subsequently improves theoretical ∆Hf values to give a 0.81 kcal molˉ¹ mean absolute deviation with ccCA-CBS-2. The ccCA-CBS method is a viable "black box" method that can be used on systems with at least 10-15 heavy atoms.

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  • Journal of Chemical Physics, 2006, College Park: American Institute of Physics

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  • Publication Title: Journal of Chemical Physics
  • Volume: 124
  • Issue: 11
  • Pages: 17
  • Peer Reviewed: Yes

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The Scholarly Works Collection is home to materials from the University of North Texas community's research, creative, and scholarly activities and serves as UNT's Open Access Repository. It brings together articles, papers, artwork, music, research data, reports, presentations, and other scholarly and creative products representing the expertise in our university community. Access to some items in this collection may be restricted.

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  • March 17, 2006

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  • Feb. 13, 2012, 2:23 p.m.

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  • May 12, 2014, 5:03 p.m.

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DeYonker, Nathan J.; Cundari, Thomas R., 1964- & Wilson, Angela K. The correlation consistent composite approach (ccCA): An alternative to the Gaussian-n methods, article, March 17, 2006; [College Park, Maryland]. (digital.library.unt.edu/ark:/67531/metadc75421/: accessed May 30, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT College of Arts and Sciences.