Speaker: Matthieu MICOULAUT (Sorbonne Université)
Date: 1 Mars 2022, 14:00 p.m.
Place: SZFI (Building 1) auditorium and online: https://wigner-hu.zoom.us/j/99986198653?pwd=elpKaGRaMVpmbGFGNGxLZFRrVGt…
Meeting ID: 999 8619 8653
Passcode: 304942
Title: Rigidity transitions in network glasses
Abstract:
If crystallization can be avoided during cooling, a liquid will display a substantial increase of its viscosity, and will form a glass that behaves as a solid with a relaxation time that grows exponentially with decreasing temperature. Given this ‘off-equilibrium’ nature, a hysteresis loop appears when a cooling/heating cycle is performed across the glass transition.
We will discuss this salient phenomenology in the context of flexible-to-rigid transitions by using molecular dynamics simulations. We find that for certain systems, minuscule thermal changes are found and reveal glasses of ‘thermally reversible’ character with optimal volumetric or enthalpic recovery. The analysis of the topology of the atomic network structure shows that corresponding liquids adapt under increasing stress. The analysis of the dynamic behaviour indicates that the structural relaxation time is substantially reduced in these adaptive liquids, and also drives the reversible character of the glass transition. Ultimately, the results substantiate the notion of stress-free (Maxwell isostatic) rigidity in disordered molecular systems, while also revealing new implications for the topological engineering of e.g. phase change materials.
