Theoretical studies of glassy relaxation

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:6976153

Ye, J

In the first chapter, the author briefly reviews glassy materials and the glass transition, and discusses concepts concerning the glass transition and glass dynamics. The author discusses various models and essential ingredients for glassy relaxation. Through studying several generic models, it is demonstrated that the concept of constrained dynamics is extremely useful in understanding glassy relaxation. Particularly, the author studies diffusion on a diluted hypercube as a generic model which only involves dynamics and constraints. The author focuses on understanding the ubiquity of the stretched exponential relaxation. In the chapter 3, diffusion on random graphs is studied. It is shown analytically that the relaxation follows a stretched exponential law with exponent [beta] = 1/3 in the giant cluster and with [beta] = 2/5 for the finite clusters. In chapter 4, the process is studied of a test particle escaping over a fluctuating barrier as a model for the gating process in viscous liquids. This model exhibits a considerable non-Arrhenius temperature dependence for the mean exit time if a temperature dependent correlation time is introduced. In chapter 5, the author considers diffusion in rugged landscapes. Considering equipartition of energy, it is found that there are only three possible temperature dependences: A Vogel-Fulcher law, a strong non-Arrhenius law, or an Arrhenius law. In chapter 6, constrained diffusion is studied on hard-square lattices it an effort to understand the possible connection between the stretched exponential relaxation in time and the Vogel-Fulcher law for relaxation times. It is found that many physical quantities, including the diffusion coefficient and the transition rate, follow the Doolittle formula. The waiting time distribution follows an inverse power law in the high particle concentration region. This is a form often employed for deriving the stretched exponential relaxation.

• Research Organization: Duke Univ., Durham, NC (United States)
• OSTI ID: 6976153
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602* -- Other Materials-- Structure & Phase Studies
664000 -- Atomic & Molecular Physics-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
FOUR-DIMENSIONAL CALCULATIONS
GLASS
MATHEMATICAL MODELS
ORDER-DISORDER TRANSFORMATIONS
PHASE TRANSFORMATIONS
RELAXATION