The computation of the potential energy surface for H2 + OH → H2O + H using ab initio and density functional theory methods

✍ Scribed by Branko S. Jursic

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 137 KB
• Volume: 62
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1997)62:6<639::aid-qua6>3.0.co;2-x

✦ Synopsis

The reaction energy profile for H q OH ¬ H q H O was computed 2 2 using HF, MP2, MP4, QCISD, G1, G2, and G2MP2 ab initio methods. In addition, the Ž . B3LYP, B3P86, B3PW91, BLYP, BP291, and SVWN density functional theory DFT methods were also used. All the ab initio methods, with the exception of the G series, produced much higher activation barriers and heats of reaction than the experimental values. On the other hand, the DFT methods produced negative forward and reverse barriers which were too low, with the exception of the hybrid DFT methods. The G2 ab initio method generated energies which deviated from the experimental values by ; 1 kcalrmol and therefore should be considered a very accurate computational method. The hybrid DFT methods produced positive forward reaction barriers with energies that were 2᎐4 kcalrmol lower than the experimental values. The geometries of the transition state and energies computed by the ab initio and DFT methods were compared. These results suggest that, in the hybrid exchange functional, the portion of the Slater exchange term should be increased. This may be the reason why the computed energies were too low.