Understanding diffraction from disordered materials: toward the analysis beyond the intermediate-range order

The construction of large quantum beam facilities such as synchrotron radiation and high-intensity proton accelerator facilities has provided access to high-intensity, high-energy quantum beams that are indispensable for the structural analyses of disordered materials via diffraction measurements. By the complementary use of X-rays, which are sensitive to heavy elements, and neutrons, which are sensitive to light elements, along with the advances in computer simulations and topological analysis techniques, we have achieved a deep understanding of the intermediate-range structure of disordered materials. In this review, we introduce the recent results obtained by the complementary use of X-ray and neutron diffraction. In particular, we discuss the differences among tetrahedrally coordinated disordered materials in comparison with dense random packing metallic glass to understand the origin of the three-peak structure, the first sharp diffraction peak (FSDP, Q 1), principal peak (PP, Q 2), and Q 3 observed in quantum beam diffraction data. Moreover, we demonstrate that comparing persistent homology analysis data with the ring size distributions of silica (SiO2) glass and crystals is important for understanding the low-energy excitations observed in inelastic neutron scattering data.