fragilisons

Fragilisons are a proposed class of ultra-light, metastable crystalline materials conceived in theoretical discussions of fragile glass formers. The term blends fragilis, Latin for fragile, with a common suffix used for material names. In this context, fragilisons are used as model systems to explore how nanoscale structure governs dynamical fragility near the glass transition.

They are envisioned as layered films with weak interlayer bonding and highly directional networks, potentially realized in oxide or chalcogenide chemistries. Synthesis methods include vapor deposition and pulsed laser deposition on ceramic or semiconductor substrates, with control over thickness down to the nanometer scale. Their unit cells typically display anisotropic bonding, yielding high in-plane stiffness while enabling facile crack propagation perpendicular to the layers.

Key properties include extreme brittleness at ambient temperatures, rapid crystallization upon heating, and strong sensitivity of mechanical response to small thermal or compositional changes. Fragility can be quantified by a fragility parameter that correlates with yield strength and fracture toughness as a function of temperature. Optically, fragilisons may exhibit a high refractive index and wide bandgap, making them of interest for coatings, though their brittleness constrains long-term reliability.

Applications are mainly research-oriented: they provide a platform for testing theories of glass transition dynamics, calibrating computational models of nanoscale fracture, and studying the interplay between structure, dynamics, and failure in ultra-thin films. Handling requires standard ceramic powder safety practices, with attention to brittle fracture and dust control. While not produced for commercial devices, fragilisons occupy a niche in materials science as a conceptual tool for understanding fragility in condensed matter.