Embedding techniques for irradiation-induced defects in crystalline SiO2

We present a new atomistic embedding technique for neutral and charged defects in silicon dioxide and apply it to the neutral vacancy and the crystalline analog of the E´_γ defect, the E´₁ in α-quartz. We show that there are significant relaxations up to 8 Å away from the vacancy and that this realization points to the necessity of using much larger unit cells in solid state DFT calculations. Also, we have shown that the long-range Madelung field alters estimates of hyperfine interactions significantly. In fact, the current embedding scheme has led to greatly improved predictions for ²⁹Si hyperfine interactions for the E´₁ center.