Real and reciprocal space structural correlations contributing to the first sharp diffraction peak in silica glass

We have applied a 'real-reciprocal space analysis', using the continuous wavelet transform technique, to the experimental neutron and x-ray structure factors of silica glass to elucidate a correlation between the 'first sharp diffraction peak (FSDP)' in reciprocal space and the corresponding length scale in real space. The present analysis allows us to obtain compelling evidence that the dominant interatomic distance linked to the FSDP in silica glass is ∼5 A, although longer distances are also important, making an exponentially decreasing contribution. Further analysis using molecular-dynamics simulations demonstrates that the interatomic spatial correlations at r∼5 A are associated with a couple of local 'pseudo-Bragg' planes having an interlayer separation of ∼4 A, accounting for the origin of structural ordering on the medium-range length scale in silica glass