A quantum mechanical study of the structure, vibrational spectra and relative energetics of XOOI, XIO2 and XOIO (X = Cl, Br, I) isomers

Two different effective-core-potential methodologies, augmented by extra po larization functions were used at the MP2 and CCSD(T) levels of theory to i nvestigate a number of iodine containing isomers of the type XOOI, XIO2 and XOIO (X = Cl, Br, I). The procedures, successfully tested first on the wel l studied Cl2O2 system, produced results for XIO2 isomers analogous to the corresponding Cl and Br species. The relative energetics however, indicates competing stability depending on the method, between the peroxide XOOI and the Y-shaped XIO2 form for ClIO2 and BrIO2 and between IOOI and IOIO for t he I2O2 family. (C) 2001 Elsevier Science B.V. All rights reserved.