A NEW CLASS OF FREE STABLE DOUBLY NEGATIVE SYSTEMS - 3 SI2O52- ISOMERS AND THEIR INTERCONVERSION

The free dianionic Si2O52- system is studied by standard ab initio met hods. We have located three distinct isomers in the Si2O52- system. Al l three Si(2)O(5)2(-) isomers are found to be thermodynamically stable with respect to dissociation into monoanionic fragments. However, onl y two of them are predicted to be clearly stable with respect to verti cal electron autodetachment. Minimal energy pathways which interconnec t the three isomers have been studied together with the binding energy of the excess electron along them. The results give rise to an unusua l nuclear dynamics problem. In particular, the associated barriers hav e been found to be high and wide enough to predict long lifetimes for two free dianionic species. (C) 1996 American Institute of Physics.