Are glasses different in Flatland? Insights from a model of 2d amorphous silica"
Dr. Marco Dirindin
Department of Physics, University of Trieste (Italy)

Over the last 20 years, the study of low-dimensional systems has been extremely prolific, giving rise to new technological applications and developments for fundamental research. Despite the vast knowledge we now have about two-dimensional crystalline materials, little is known about their amorphous counterparts. In this talk, I will discuss the structure and dynamics of a simple model of the silica bilayer, one of the first two-dimensional amorphous materials ever synthesized. We use a structure-matching approach to improve the effective potential used to describe the system [2], focusing on the reproduction of the network structure of the experimental samples. We then carefully study the dynamics of the optimized model, paying particular attention to the peculiarities of two-dimensional materials, such as Mermin-Wagner fluctuations. At low temperatures, the system behaves like a highly viscous liquid, with heterogeneous dynamics and relaxation times that follow an Arrhenius law. Surprisingly, we observe a concomitant appearance of transient crystallites, which at the lowest accessible temperature are nanometric in size [2]. These results, which have little correspondence in three-dimensional amorphous systems, shed new light on the physics of two-dimensional network-forming materials.

[1] P. K. Roy, M. Heyde, A. Heuer, Phys. Chem. Chem. Phys. 20, 14725 (2018)
[2] M. Dirindin, D. Coslovich, J. Phys. Chem. B 129, 1095 (2025)