Experimental test of a predicted dynamics–structure–thermodynamics connection in molecularly complex glass-forming liquids
[1];
- Department of Materials Science, University of Illinois at Urbana–Champaign, Urbana, IL 61801,, Material Research Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801,
- Department of Materials Science, University of Illinois at Urbana–Champaign, Urbana, IL 61801,, Material Research Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801,, Department of Chemistry, University of Illinois at Urbana–Champaign, Urbana, IL 61801
Understanding in a unified manner the generic and chemically specific aspects of activated dynamics in diverse glass-forming liquids over 14 or more decades in time is a grand challenge in condensed matter physics, physical chemistry, and materials science and engineering. Large families of conceptually distinct models have postulated a causal connection with qualitatively different “order parameters” including various measures of structure, free volume, thermodynamic properties, short or intermediate time dynamics, and mechanical properties. Construction of a predictive theory that covers both the noncooperative and cooperative activated relaxation regimes remains elusive. Here, we test using solely experimental data a recent microscopic dynamical theory prediction that although activated relaxation is a spatially coupled local–nonlocal event with barriers quantified by local pair structure, it can also be understood based on the dimensionless compressibility via an equilibrium statistical mechanics connection between thermodynamics and structure. This prediction is found to be consistent with observations on diverse fragile molecular liquids under isobaric and isochoric conditions and provides a different conceptual view of the global relaxation map. As a corollary, a theoretical basis is established for the structural relaxation time scale growing exponentially with inverse temperature to a high power, consistent with experiments in the deeply supercooled regime. A criterion for the irrelevance of collective elasticity effects is deduced and shown to be consistent with viscous flow in low-fragility inorganic network-forming melts. Lastly, implications for relaxation in the equilibrated deep glass state are briefly considered.
- Research Organization:
- Univ. of Illinois at Urbana-Champaign, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
- Grant/Contract Number:
- SC0020858
- OSTI ID:
- 1780534
- Alternate ID(s):
- OSTI ID: 1781645
- Journal Information:
- Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Vol. 118 Journal Issue: 18; ISSN 0027-8424
- Publisher:
- Proceedings of the National Academy of SciencesCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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