Calculated barrier heights for OH + C/sub 2/H/sub 2/ and OH + C/sub 2/H/sub 4/ using unrestricted Moeller-Plesset perturbation theory with spin annihilation

Journal Article · Wed Jul 08 04:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00248a012· OSTI ID:5954146

Sosa, C; Schlegel, H B

The reactions of OH radical with C/sub 2/H/sub 2/ and C/sub 2/H/sub 4/ have been studied with ab initio molecular orbital techniques. Reactants, loose clusters, transition structures, and products were optimized at UHF/3-21G and UHF/6-31G*. The barrier heights have been computed by using unrestricted Hartree-Fock and Moeller-Plesset perturbation theory up to fourth order, including single, double, and quadruple excitations. Spin contamination in the UHF wave function has been corrected by annihilating the largest spin contaminant. The vibrational frequencies were computed by using analytical derivative methods at the UHF/3-21G level. The barrier heights for both reactions are overestimated by 7-15 kcal/mol at the UMP2, UMP3, and UMP4 levels. Annihilation of the largest spin contaminant lowers the barrier heights by 7-15 kcal/mol. Calculations at the PMP4/6-31G* level are in good agreement with the estimated experiment barrier heights.

• Research Organization: Wayne State Univ., Detroit, MI
• OSTI ID: 5954146
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:14; ISSN JACSA
• Country of Publication: United States
• Language: English

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