DENSITY-FUNCTIONAL STUDY OF CHLORINE-OXYGEN COMPOUNDS RELATED TO THE CLO SELF-REACTION

Geometrical parameters, vibrational frequencies, relative stabilities, and dissociation energies of the three stable Cl2O2 isomers and the O ClO and ClOO radicals were investigated by density functional theory ( DFT). The present analysis shows that DFT using hybrid functionals is capable of describing these systems to at least the same degree of acc uracy as ab initio methods. The average absolute bond-length deviation of ClClO2,, ClOOCl, and ClO2, from experimental results is 0.024/0.02 7 Angstrom, with a maximum deviation for the dichlorine peroxide O-O b ond equal to 0.072/0.063 Angstrom, for the B3PW91 and B3LYP functional s, respectively. The average absolute bond-angle deviation for the hyb rid functionals is 0.8 degrees. Harmonic vibrational frequencies calcu lated with DFT give for all Cl-O compounds good agreement with experim ents. The dissociation energies of ClOOCl, OClO, and ClOO were found t o be in good agreement with experiments, the average error being less than 1.2 kcal/mol. The two isomers chloryl chloride (ClClO2,) and dich lorine peroxide (ClOOCl) were found to be approximately 9 kcal/mol mor e stable than the chlorine chlorite (ClOClO) isomer. The ClOO isomer i s predicted to be 3.0 kcal/mol more stable than OClO, in accordance wi th the experimental value of 4 kcal/mol. (C) 1998 John Wiley & Sons, I nc.