How fractals jam glassy materials

Unlike molecules in a crystal lattice, the molecules in glass don’t have regular positions, even though glass is a solid. Scientists think that glass molecules don’t flow, as they would in a liquid, because the particles are caged by each other and don’t have enough energy to overcome a threshold known as the energy barrier, which is like a hill. Instead, the molecules stay in valleylike depressions.

But the energy landscape of glass molecules may not be as simple as hills and valleys, scientists argue April 24 in Nature Communications. As the molecules are compressed, the valleys break down into geometric patterns known as fractals. The finding could help explain what happens when glassy materials are deformed or when coffee beans in a container jam, the scientists say.