Modeling disorder in amorphous silica with embedded clusters: The peroxy bridge defect center

摘要: We use quantum-mechanical modeling to study the effect of local and long-range disorder on incorporation energy, optical, IR, XPS spectra a peroxy linkage defect in amorphous silica (a-SiO2). discuss methods simulate structures investigate which extent cluster models are applicable a-SiO2. For this purpose we compare results periodic DFT calculations possible linkages formed incorporating an oxygen atom super-cell with obtained using molecular embedded models. simple clusters terminated by H atoms larger treated ONIOM technique, distortion structure surrounding is accounted for region approximately 15 Angstrom. The demonstrate importance medium-range around defect, such as center, induces relaxation area extending beyond first second neighbors. geometric distribution energies cannot be adequately described model. On other hand, optical transitions localized -O-O- bridge itself not strongly affected disorder. Our indicate that approaches, ONIOM, can provide useful alternative fully ab initio geometrical point defects silica.