Oxygen 2p partial density of states and bond angles around O atoms in SiO 2 glass

The valence- and conduction-band O 2p partial densities of states (DOSs) in a typical oxide glass, SiO2, and the corresponding alpha-quartz crystal were investigated by soft X-ray emission spectroscopy and soft X-ray absorption spectroscopy, respectively. Both of the obtained spectra for glassy and crystal SiO2 surprisingly resemble each other, indicating closely similar local environments around the O atoms, in particular suggesting an average Si-O-Si bond angle of similar to 150 degrees. Ab initio molecular dynamics (MD) simulations were carried out, and the above experimental results were confirmed from the bond angle dependence of the O 2p partial DOS obtained from the ab initio MD simulation.