Formation energy of threefold coordinated oxygen in SiO2 systems

Using density functional calculations in the generalized gradient approxima tion, the excitation energy for the formation of a threefold coordinated ox ygen atom is evaluated. The bistable E-1' defect of alpha-quartz in the neu tral charge state is used as a model system. The puckered configuration whi ch shows a threefold coordinated oxygen center together with a doubly occup ied silicon dangling bond is found to be at 2.7 eV higher energy than the S i-Si dimer configuration. (C) 2000 Elsevier Science B.V. All rights reserve d.