We investigate molecular scale mechanisms for radiation-induced release of hydrogen from precursor sites using density functional theory applied to a fully periodic model of SiO2. We focus on proton release from H-decorated oxygen vacancies in the bulk oxide. After hole-capture at the vacancy, a proton can hop to an energetically favorable bound state at a neighboring oxygen atom. In α-quartz, this release mechanism has an activation energy of about 1.2 eV. In amorphous silica, this hop has a range of low barriers, from 0.1 to 0.5 eV. Furthermore, another proton release mechanism involves cracking of H2 molecules by a reaction with an isolated, positively charged Si-dangling bond.
|Original language||English (US)|
|Number of pages||5|
|Journal||Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms|
|Issue number||1-2 SPEC. ISS.|
|State||Published - Sep 1 2006|
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics