Radiation induced defect creation or revelation in metal oxide-semiconductor (MOS) field effect transistors (FET) or bipolar structures remains a hazard for devices exposed to hostile environments such as those encountered in space. Certainly for MOSFETs and to some degree for bipolar transistors, defects generated in thin, amorphous SiO/sub 2/ layers are of prime concern. Despite extensive experimental studies one can reasonably say that a complete theoretical description of any point defect in SiO/sub 2/ is lacking. We report the first ab initio quantum mechanical investigation of the structure of the E'/sub /spl delta// center in amorphous SiO/sub 2/ (a-SiO/sub 2/). Our calculations suggest that the unpaired electron is shared by only two Si atoms, irrespective of the Si cluster size.