1ST SHARP DIFFRACTION PEAK AND INTERMEDIATE-RANGE ORDER IN AMORPHOUS SILICA - FINITE-SIZE EFFECTS IN MOLECULAR-DYNAMICS SIMULATIONS

Large-scale molecular dynamics simulations of amorphous silica are carried out on systems containing up to 41 472 particles using an effective interatomic potential consisting of two-body and three-body covalent interactions. The intermediate-range order represented by the first sharp diffraction peak (FSDP) in the neutron static structure factor shows a significant dependence on the system size. Correlations in the range 0.4-1.1 nm are found to play a vital role in determining the shape of the FSDP correctly. The calculated structure factor for the largest system is in excellent agreement with neutron diffraction experiments, including the height of the FSDP.