Embedding techniques for irradiation-induced defects in crystalline SiO/sub 2/

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/sub /spl gamma//' defect, the E/sub 1/' in /spl alpha/ quartz. We show that there are significant relaxations up to 8 /spl Aring/ away from the vacancy and that this points to the necessity of using much larger unit cells in solid-state density functional theory (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 /sup 29/Si hyperfine interactions for the E/sub 1/' center.