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


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

Creation Date: March 17, 2006
UNT College of Arts and Sciences
UNT Scholarly Works
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Creator (Author):
DeYonker, Nathan J.

University of North Texas

Creator (Author):
Cundari, Thomas R., 1964-

University of North Texas

Creator (Author):
Wilson, Angela K.

University of North Texas

Publisher Info:
Place of Publication: [College Park, Maryland]
  • Creation: March 17, 2006

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

Department: Chemistry

Copyright 2006 American Institute of Physics. J. Chem. Phys. 124, 114104 (2006);


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.

Physical Description:

17 p.

Keyword(s): composite methods | correlation consistent composite approachs | ccCA
Source: Journal of Chemical Physics, 2006, College Park: American Institute of Physics
UNT College of Arts and Sciences
UNT Scholarly Works
  • DOI: 10.1063/1.2173988 |
  • ARK: ark:/67531/metadc75421
Resource Type: Article
Format: Text
Access: Public
Publication Title: Journal of Chemical Physics
Volume: 124
Issue: 11
Pages: 17
Peer Reviewed: Yes