The solid backbones of amorphous nanoporous aerogels (such as silica and silicate networks) lack long-range crystalline order, exhibiting disordered glassy network structures. Within these non-crystalline networks, atomic-level topological defects—such as bond-angle distortions and bond-length stretching between silicon-oxygen tetrahedra ($text{SiO}_4$), strained three- and four-membered rings, and uncoordinated dangling bonds—dictate physical responses under thermal and mechanical fields. Investigating the glassy dynamics of disordered aerogel networks provides insight into thermodynamic relaxation in confined non-crystalline solids.

A characteristic feature of glassy dynamics is its complex potential energy landscape and non-Debye relaxation behavior. Because aerogel frameworks contain spatial steric hindrances and topological defects, localized atoms subjected to thermal fluctuations or mechanical stresses do not undergo simple harmonic vibrations. Instead, they execute thermally activated hopping transitions across potential energy barriers or cooperative rearrangements (CRRs) to achieve structural relaxation.

This relaxation process exhibits dynamic hysteresis and aging effects. At low temperatures or under high-frequency mechanical fields, topological defects and low-energy excitation states (Two-Level Systems, TLS) govern the specific heat anomalies and phonon scattering behaviors of aerogels. By combining dielectric spectroscopy and ultrasonic attenuation measurements with molecular dynamics simulations, physicists characterize the dynamic freezing and thawing of localized atomic clusters within amorphous aerogel networks near the glass transition temperature.