Calculation of relative concentrations of E′ centres in amorphous silica

Abstract We have used two different ideal continuous random network structures to model a-SiO2, and the embedded cluster method to study the structure and relative concentrations of E′ type centres in a-SiO2. We assume that E′ centres can be formed at any site of the amorphous structure with equal probability and find a good correlation between the average Si–O distance at a particular oxygen site and the hyperfine splitting on the Si nuclei of the formed E′ centre. Using this correlation we find the relative concentration of dimer type E δ ′ and dangling bond type E γ ′ centres of about 1:4. We estimate that only 10% of Eγ centres will have the structure similar to that of puckered E1 centre in α-quartz.