Gaussian-3 (G3) theory for molecules containing first and second-row atoms

Journal Article · Sun Nov 01 00:00:00 EST 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.477422· OSTI ID:663683

Curtiss, L A ^[1]; Raghavachari, K ^[2]; Redfern, P C ^[1]; Rassolov, V; Pople, J A ^[3]

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1. Chemistry and Materials Science Divisions, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
2. Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974 (United States)
3. Department of Chemistry, Northwestern University, Evanston, Illinois 60208 (United States)

Gaussian-3 theory (G3 theory) for the calculation of molecular energies of compounds containing first (Li{endash}F) and second row (Na{endash}Cl) atoms is presented. This new theoretical procedure, which is based on {ital ab initio} molecular-orbital theory, modifies G2 theory [J. Chem. Phys. {bold 94}, 7221 (1991)] in several ways including a new sequence of single point energy calculations using different basis sets, a new formulation of the higher level correction, a spin{endash}orbit correction for atoms, and a correction for core correlation. G3 theory is assessed using 299 energies from the G2/97 test set including enthalpies of formation, ionization potentials, electron affinities, and proton affinities. This new procedure corrects many of the deficiencies of G2 theory. There is a large improvement for nonhydrogen systems such as SiF{sub 4} and CF{sub 4}, substituted hydrocarbons, and unsaturated cyclic species. Core-related correlation is found to be a significant factor, especially for species with unsaturated rings. The average absolute deviation from experiment for the 148 calculated enthalpies of formation is reduced to under one kcal/mol, from 1.56 kcal/mol for G2 theory to 0.94 kcal/mol for G3 theory. Significant improvement is also found for ionization potentials and electron affinities. The overall average absolute deviation of G3 theory from experiment for the 299 energies is 1.02 kcal/mol compared to 1.48 kcal/mol for G2 theory. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 663683
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 18 Vol. 109; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
AFFINITY
ELECTRONEGATIVITY
ELECTRONIC STRUCTURE
FORMATION HEAT
IONIZATION POTENTIAL
MOLECULAR ORBITAL METHOD