It was recalled that the neutral O vacancy in SiO2 was an archetypal intrinsic defect. A study was made of the marked effects of lattice relaxation upon the structure and properties of this defect in both pure and Ge-doped α-quartz by using a hybrid classical ab initio embedded-cluster method. The neutral vacancy induced very strong and anisotropic lattice distortion. At the vacancy site, the Si-Si distance in α-quartz relaxed to the same spacing as in elemental Si. The long-range distortion components extend further than 13Å from the vacant site. The displacements of surrounding atoms were strongly asymmetric with respect to the vacancy, contrary to previous theoretical results. A strong relaxation in the lowest triplet excited state of the vacancy was predicted, and a small (less than 1eV) triplet luminescence energy. A strong dependence of the defect properties upon the radius of the relaxed region was demonstrated.

Asymmetry and Long-Range Character of Lattice Deformation by Neutral Oxygen Vacancy in α-Quartz. V.B.Sulimov, P.V.Sushko, A.H.Edwards, A.L.Shluger, A.M.Stoneham: Physical Review B, 2002, 66[2], 024108 (14pp)