Uchino, Takahashi, and Yoko (UTY) had recently proposed a model for the Eγ’ center of amorphous silica. Their model successfully accounts for several previously unexplained characteristics of this defect. One of the structures from which UTY derive their model for the Eγ’ center was a neutral edge-sharing pair of SiO4 tetrahedra, which had lost one of its bridging O atoms. However, the precursor (the intact edge-sharing pair Si2O6) had yet to be confirmed by experimental studies of amorphous silica. Theoretical support for the UTY model was found here. Using ab initio molecular-dynamics simulations, it was possible to reproduce an edge-sharing pair. By removing an O and an electron from this structure, and optimizing the geometry, the UTY model was confirmed for the Eγ’ structure; providing independent support in its favor.

Edge-Sharing Tetrahedra - Precursors of the Eγ’ Defects in Amorphous Silica. M.M.G.Alemany, J.R.Chelikowsky: Physical Review B, 2003, 68[5], 054206 (4pp)