[formula presented] centers in [formula presented] quartz in the absence of oxygen vacancies: A first-principles molecular-dynamics study

Abstract

The displacement of an oxygen atom in pure [Formula presented] quartz is studied via first-principles molecular dynamics. The simulations show that when an O atom in a Si-O-Si bridge is moved away from its original equilibrium position, a new stable energy minimum can be reached. Depending on the spin state and charge [Formula presented] of the system, this minimum can give rise to either a threefold oxygen (singlet ground state and [Formula presented]) or to an unsaturated Si atom carrying a dangling bond (triplet state). In the latter case, the hyperfine parameters associated with the [Formula presented] dangling bond are in rather good agreement with electron paramagnetic resonance/electron nuclear double resonance experiments. © 2003 The American Physical Society.