Emergence of equilibrated liquid regions within the glass

• DOI: 10.1038/s41567-022-01791-w
• Publication Date: 2022-10-24T16:03:59Z
• Authors: Ana Vila-Costa; Marta Gonzalez-Si...; Cristian Rodrígue...; Marta Rodríguez-L...; Javier Rodriguez-...
• Keywords: Applied physics; Phase transitions and critical phenomena; Glasses; 0103 physical sciences; 01 natural sciences

Peer reviewed<br/>J.R.-V. and M.G.-S. acknowledge grant MAT2016-79759-R funded by MCIN/AEI/ 10.13039/501100011033 and ‘ERDF A way of making Europe’, and grant PID2020-117409RB-I00 funded by MCIN/AEI/10.13039/501100011033. C.R.-T. is a Serra Hunter Fellow. The ICN2 was funded by the CERCA programme/Generalitat de Catalunya. The ICN2 was supported by the Severo Ochoa Centres of Excellence Programme, funded by the Spanish Research Agency (AEI, grant no. SEV-2017-0706).<br/>The conventional understanding of the glass transition is that the transition from glass to liquid appears as a dynamic process in which atoms or molecules relax cooperatively into the equilibrium phase. Here we show that—in contrast to this picture—isolated regions of liquid form within the glassy matrix and the nature of the glass transition at a given temperature depends on the ratio between the relaxation time of the glass, τglass, and the alpha relaxation time of the equilibrated liquid, τα. At temperatures at which τglass/τα is large, we observe that high-mobility regions transit directly into the equilibrated liquid and subsequently grow by dynamic facilitation before—or while—cooperative glass relaxation sets into play. On the contrary, at temperatures associated with smaller τglass/τα, the glass transition proceeds by cooperative relaxation dynamics throughout the material. This behaviour is independent of the experimental procedure or protocol used to produce the glass.<br/>