Density functional theory study of self-trapped holes in disordered SiO2

The structures of self-trapped holes (STHs) in a disordered SiO2 network are investigated using first-principles calculations. We consider two different kinds of STHs: STH1, consisting of a hole trapped on an oxygen atom bridging two silicon atoms, and STH2, a metastable structure, in which the hole is delocalized over two bridging oxygen atoms. Using density functional theory and a self-interaction correction scheme, we fully optimize the structural model in an unbiased way and are able to reproduce, for the first time, the experimentally observed STH2 at a density functional theory level and without applying any geometrical constraint to the system. In addition, extensive molecular-dynamics simulations (similar or equal to 200 ps) are performed in order to describe the hopping of a hole within the dioxide network.