VIBRATIONAL-SPECTRUM AND STRUCTURE OF THE K2O2 COMPLEX IN SOLID ARGON- A FAR-INFRARED AND DENSITY-FUNCTIONAL THEORY STUDY

New fundamental K-O stretching frequencies of the isolated potassium p eroxide K2O2 molecule are reported for different isotopic species. The B-2u vibration can be measured for (K2O2)-K-39-O-16, (K2OO)-K-39-O-16 -O-18, (K2OO)-O-17-O-18, (K2O2)-K-39-O-18, (KKO2)-K-39-K-41-O-16 and ( KKO2)-K-39-K-41-O-18. The B-3u vibration can be located for (K2O2)-O-1 6, (K2OO)-O-16-O-18 and (K2O2)-O-18 products, and the formerly B-3g sy mmetry motion, IR-activated by symmetry breaking in (K2OO)-K-39-O-16-O -18, (KKOO)-K-39-K-41-O-16-O-18, (KKO2)-K-39-K-41-O-16, and (KKO2)-K-3 9-K-41-O-18, is equally observed. The self-consistency of the attribut ions is based on semiempirical quadratic force field calculations, and , more importantly, upon theoretical ab initio and Density Functional Theory calculations. The ground state geometry calculated using the al l electron density functional theory method corresponds to a slightly out of plane distorted rhombic structure (C-2v symmetry), in contrast to the D-2h Symmetry structure calculated for Li2O2 or at the SCF leve l for K2O2. The energy difference between rhombic D-2h and out-of-plan e C-2v structure is nevertheless too small (0.08 kcal/mol) to exclude a calculation artefact. The agreement between the positions of observe d vibrations and the density functional theory calculation predictions is however remarkable. (C) 1995 American Institute of Physics.