First sharp diffraction peak in silicate glasses: Structure and scattering length dependence

The source of the experimentally observed anomalous behavior of the first sharp diffraction peak (FSDP) in lithium silicate glasses was determined using classical molecular dynamics simulations. Partial structure factors obtained from simulations were used to investigate the sensitivity of the total structure factor to the scattering length of alkali ions. The result clearly establishes that the major difference of the FSDP between lithium and sodium disilicate glasses is due to the negative scattering length of lithium ions. Additionally, it was determined that the unusual intense FSDP in lithium silicate glass has little to do with differences of the medium-range structure in these glasses.