Prediction of the X-ray absorption near edge structure of the new high-density phase of SiO2

The X-ray absorption near edge structure (XANES) of the newly predicted high density phase of SiO2 has been calculated using a state-of-the-art supercell method including the core-hole effect. It is shown that the spectra are unique and have little resemblance to those of low density alpha-quartz and high density stishovite. It is demonstrated that the interpretation of XANES based purely on the coordination shell argument is oversimplified. Crystal symmetry and effects beyond the second nearest neighbour must be taken into consideration.