Ring size distribution in silicate glasses revealed by neutron scattering first sharp diffraction peak analysis

Silicate glasses have no long range order and a short range order similar to their crystalline counter-parts. Therefore, their key structurally distinct information lies in the medium range. The statistics of rings, describing the 3D connection of tetrahedral units, is a crucial indicator of the medium range structure. However, no experimental techniques have succeeded in quantifying the ring statistics. Here we show a heuristic method to extract ring structure information from the first sharp diffraction peak (FSDP) of the neutron scattering structure factor. We demonstrate that, for 81 commercially important silicate glasses, the real space representation I(r)-s of their FSDPs, can be consistently represented by a sum of three compressed exponentially decaying sine functions with three fixed periodicities. We propose these three characteristic periodicities are commensurate with the statistically averaged sizes of 5_ 4-, 5- and 6-membered rings, with their relative amplitudes reflecting the relative fractions. Our results are validated using Molecular Dynamics simulated glass structures. The derived ring structure information provides an insight into the structural origin of the anomaly in hardness of aluminosilicate glasses.