Although glasses exhibit disordered atomic structures, X-ray and neutron scattering reveal a subtle periodicity. Researchers at the University of Tsukuba have demonstrated that this hidden periodicity—referred to as “invisible order”—plays a critical role in determining vibrational fluctuations in the terahertz (THz) frequency range, which significantly influence the physical properties of glass.

The research is published in the journal Scientific Reports.

At first glance, glass appears to be a random network of atoms. However, X-ray and neutron beam analysis reveals a faint but consistent periodic feature known as the first sharp diffraction peak (FSDP).