Revealing the Hidden Mechanism of Room Temperature Relaxation in Glasses

ended

Glassmakers have known since ancient times that rapid cooling of a viscous liquid makes it stop flowing and transition into a solid glass state. Glasses are not in thermodynamic equilibrium and consequently their properties change over time as the structure relaxes toward a lower energy state. At room temperature (RT), the glass state is believed to be frozen and remain almost forever (>10^10 years). However, recent stain measurements on aluminosilicate glasses have shown that the dynamics are not fully arrested at RT. That is, RT relaxation occurs and leads to changes in glass volume and enthalpy, thus challenging the current consensus on glass relaxation. In this project, we will decipher the linkage between structure and RT relaxation in selected glasses with different types of chemical bonding. The aim is to reveal the hidden structural mechanism behind RT relaxation. To this end, we will first elucidate the composition dependence of RT relaxation modes and subject the glasses to varying degree of relaxation to identify the crossover temperature of relaxation modes. Then the structural evolution associated with relaxation will be tracked and the corresponding atomic configurations will be constructed. Finally, we will perform rigidity and energy landscape analyses to reveal the connection between glass network topology and propensity toward RT relaxation. The project builds on complementary expertise of the fellow applicant (structure characterization, atomistic simulations) and supervisor (relaxation, glass science). Together with the research and training environment provided by the host organization (Aalborg University, Denmark), this will ensure the achievement of this timely and innovative project as well as the dissemination and exploitation of the expected results. The research outputs will deepen our understanding of glass relaxation. The fellow applicant will emerge from the project with new skills, and the capability to launch his own research group.