Configuration interaction calculations of the structure and energetics of the high symmetry isomers of the O+4 cation

✍ Scribed by J.Barrie Peel

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 450 KB
• Volume: 218
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(94)00003-4

✦ Synopsis

The identification of the oxygen dimer cation, 0 z, by cryogenic matrix-isolation IR and ESR spectroscopies, and as the important core-cation in the ionization of gas-phase O2 clusters, has led to theoretical investigations of the stable isomeric structures available to this species. The open-shell quartet spin state favoured by 0: together with its highly symmetric structures means that ab initio all-electron calculations are bedevilled by difficulties including spin contamination, symmetry breaking and configurational convergence. The QCISD(T) approximation used in the calculations reported here seems to account for these computational problems. The 4B, state of the trans-planar ( Csh) isomer is found to be the most stable structure, though the 4Bs, state of the rectangular ( D2,,) isomer, calculated as of 4 kcal mol-' higher energy, is so because of the influence of a large zero-point vibration energy.