First principle studies on properties of silicon-vacancy related defects in amorphous silica

The non-bridging oxygen hole center (NBOHC) can decrease the transmission efficiency of the amorphous silica (α-SiO2) material. In radiation environments, the NBOHC can be produced by both the electronic (Se) and the nuclear (Sn) energy loss processes of the radiations. The Se-related formation channels of NBOHC have been well characterized. The Sn can produce isolated silicon vacancies within α-SiO2 by knocking out silicon atoms. With first principle calculations, this work investigates the characteristics of the silicon-vacancy defective α-SiO2 cells, including atomic configuration, electronic density of state and optical absorption coefficient. The stable states of the silicon vacancy defects suggest a direct and an indirect Sn-related formation channels for NBOHC. The silicon vacancy has two stable configurations, i.e., the case I contains two NBOHC along with a peroxy linkage (POL), and the case II has two POL. Thereafter, the Se can promote the transition from POL to NBOHC.