Author ORCID Identifier:
Date of Graduation
5-2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Physics (PhD)
Degree Level
Graduate
Department
Physics
Advisor/Mentor
Oliver, William
Committee Member
Kennefick, Daniel
Second Committee Member
Fu, Huaxiang
Third Committee Member
Arnold, Mark
Fourth Committee Member
Singh, Surendra
Keywords
Fragility; Glass Physics; Glass Transistion; High-Pressure Physics; Photon Correlation Spectroscopy; Structural Relaxation
Abstract
Structural relaxation in glass-forming liquids is strongly dependent on both temperature and pressure, yet direct measurement of structural α-relaxation under multi-gigapascal compression has remained experimentally challenging. This work extends depolarized photon correlation spectroscopy (DPCS) to pressures approaching 5 GPa in a diamond anvil cell, representing the highest-pressure implementation of this technique and enabling direct measurement of the structural α-relaxation in a pure liquid at extreme compression. This capability provides access to dynamical regimes previously unexplored by photon correlation spectroscopy and establishes a platform for probing glassy dynamics at high pressure. To describe these measurements, a constrained relaxation-time surface framework is developed within the Vogel–Tammann–Fulcher equation (VTF) formalism. A polynomial pressure dependence of the fragility parameter as well as the zero-mobility temperature captures the evolution of dynamics across broad regions of thermodynamic phase space. The surfaces are constrained by atmospheric-pressure data and by an independently measured isochrone obtained using the TGP technique, in which temperature is systematically varied under pressure to trace a locus of constant relaxation time near the glass transition, thereby providing an experimental determination of the Tg(P) relation. For glycerol, the framework captures deviations from simple scaling associated with pressure-induced suppression of hydrogen bonding. For cumene, a van der Waals liquid, a pressure-modified VTF relation enforces the required high-pressure asymptotic approach to vanishing mobility. Together, these experimental and modeling developments provide a coherent framework for measuring and describing structural relaxation in glass-forming liquids under extreme compression.
Citation
Lyon, K. W. (2026). Structural Relaxation in Glass-Forming Liquids at Extreme Pressure: Photon-Correlation Spectroscopy and Constrained Thermodynamic Surface Modeling. Graduate Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/6257
