Abstract: | Ab initio and density functional theory (DFT) have been applied to predict the existence of the ONOONO molecules. Two new isomers, cis‐perp‐cis and cis‐perp‐trans ONOONO, are found to be minima on the potential energy hypersurface calculated at MP2 level with 6‐311G(d) basis set and Becke3P86 and Becke3LYP levels with the cc‐PVDZ basis set. Vibrational frequencies are calculated at the optimized structures. Calculations at both ab initio and DFT methods show that cis‐perp‐cis is energetically favored in all three O O bonded ONOONO isomers. © 1999 John Wiley & Sons, Inc. Int J Quant Chem 76: 77–82, 2000 |