On the stability of the cyclic O8 molecule

We present a refined study of some isomers of the covalently bound O8 molecule at the MP2 and CCSD levels with sequences of correlation-consistent basis sets. The previously known symmetric D4d crown structure is 28 kcal/mol more stable than the structure by Forte et al. (Phys. Lett. A 377 (2013) 801), which is a second order transition state leading to 4 O 2 ( 3 ∑ g - ) and to another lower-lying unstable cyclic structure. The O8 symmetric crown lies 104 kcal/mol above the 4 O 2 ( 3 ∑ g - ) fragments and has 1.40 Å O–O bonds, which are shorter than those of the O4 and O6 cyclic species at the MP2/CBS level.