The structure of the first sharp diffraction peak (FSDP) of amorphous silicon (a‐Si) near 2 Å−1 is addressed with particular emphasis on the position, intensity, and width of the diffraction curve. By studying a number of continuous random network (CRN) models of a‐Si, it is shown that the position and intensity of the FSDP are primarily determined by radial atomic correlations in the amorphous network on the length scale of 15 Å. A shell‐by‐shell analysis of the contribution from different radial shells reveals that key contributions to the FSDP originate from the second and fourth radial shells in the network, which are accompanied by a background contribution from the first shell and small residual corrections from the distant radial shells. The results from numerical calculations are complemented by a phenomenological discussion of the relationship between the peaks in the structure factor in the wavevector space and the reduced pair‐correlation function in the real space. An approximate functional relation between the position of the FSDP and the average radial distance of Si atoms in the second radial shell in the network is derived, which is corroborated by numerical calculations.
The static structure factor of amorphous silicon (a-Si) models, containing 400,000 atoms with a density of 2.25 g⋅cm−3, has been studied by generating atomistic models using classical molecular-dynamics simulations. The behavior of the structure factor, S(Q), in the limit Q → 0, is examined to determine the degree of hyperuniformity in a-Si and is compared with the results with those from earlier simulations and small-angle X-ray scattering experiments. The study suggests that the computed value of the relative variance of the number of atoms at large distances, and hence S(Q → 0), lies in the range from 0.00736 to 0.00758, which is very close to the experimental value of 0.0076 ± 0.0005, obtained from an extrapolation of transmission X-ray scattering data in the small-angle region. The non-zero value of the structure factor S(0) in a-Si can be attributed to density fluctuations on a very large length scale, which is a characteristic property of the structural and topological ordering of silicon atoms in the amorphous state.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.