2017 Alfred R. Cooper Award Session
Alfred R. Cooper Award Session
2-5 p.m., October 10, Room 310
Cooper Distinguished Lecture
Edgar Zanotto, Federal University of Sao Carlos
The Ultimate Fate of Glass
Glasses spontaneously start to relax toward the SCL state at any T>0 and eventually crystallize, but some (e.g., B2O3) are extremely resistant to crystallization. Whether supercooled liquids(SCLs) crystallize before or after relaxation is an open question. At the kinetic spinodal temperature, T<SUB>KS</SUB>, the average relaxation time, tR, of a SCL is equal to the average time required to form the first crystalline nucleus, tN. Above T<SUB>KS</SUB>, tR<tN, whereas for T<T<SUB>KS</SUB>, tR>tN. A very relevant outcome of this concept is that if T<SUB>KS</SUB>>T<SUB>Kauzmann</SUB>, the material would crystallize before reaching the temperature of entropy catastrophe and the Kauzmann paradox would be solved! Here we estimate values of T<SUB>KS</SUB> and T<SUB>Kauzmann</SUB> and the time required for crystallization at very low temperatures for some oxide glass-formers, but will keep these results as a surprise to the attendees. Daniel Cassar, Prabhat Gupta and John Mauro significantly contributed to these ideas.
2017 Alfred R. Cooper Young Scholar Award Presentation
Yushu Hu, University of California, Los Angeles
Glass Relaxation is Controlled by the Topology of the Atomic Network
Yushu Hu1, Tobias Bechgaard2, Morten Smedskjaer2, Mathieu Bauchy1
1Physics of AmoRphous and Inorganic Solids Laboratory (PARISlab), University of California, Los Angeles, CA 90095-1593, USA; firstname.lastname@example.org
2Department of Chemistry and Bioscience, Aalborg University, 9220 Aalborg, Denmark
Understanding, predicting, and controlling glass relaxation is of primary importance for the manufacturing of display glasses, as any small variation in volume can result in undesirable pixel misalignments. However, no clear atomistic mechanism of structural and stress relaxation is available to date, which limits our ability to identify optimal glass compositions featuring low relaxation. Here, based on modulated differential scanning calorimetry experiments and molecular dynamics simulations, we study the relaxation of a series of alkali-free calcium aluminosilicate (CAS) glasses with varying compositions. We observe that selected CAS compositions exhibit minimal relaxation. We investigate the structural origin of this behavior by means of topological constraint theory. Based on this analysis, we demonstrate that minimal relaxation is achieved for isostatic glasses, which are both free of eigenstresses and floppy modes. This highlights the crucial role of the atomic topology in controlling the propensity for glass relaxation.