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Molecular dynamics studies of metallic glasses

Citation

Lee, Hyon-Jee (2003) Molecular dynamics studies of metallic glasses. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05292003-165018

Abstract

The thermodynamic, structural, and mechanical properties of metallic glasses are studied using molecular dynamics simulations. Molecular dynamics provides a computational framework to simulate the movement of interacting atoms in response to external perturbations, such as changes in temperature or pressure. In this thesis, a Sutton-Chen potential was chosen to describe the many-body interactions in metals and alloys. Our first application for this approach is to develop a simple model to derive the thermodynamic properties of metallic alloys (Chapter 2). Based on this model, we demonstrate that the glass transition is thermodynamically sensitive to differences between atomic radii and that there is an optimal difference for glass formation. Next, we extend these simulations to elucidate the details of structural organization in the glass (Chapter 3). We find that the liquid phase is characterized by a local five-fold symmetry, which becomes more prominent as the glass phase forms. This five-fold symmetry is related to the formation of icosahedral structures. The mechanical properties of glasses are also investigated and it is found that shear localization, which accompanies a sharp drop in the stress-strain curve, occurs at 45 degree with respect to the loading axis (Chapter 4). The generation of free volume is found to be the dominant mechanism that leads to shear localization, rather than adiabatic heating. Finally, generic first principle potentials are constructed to guide the experimental development of AlTiNi based metallic glasses (Chapter 5). Together, the results from these simulations improve our understanding of the thermodynamic, structural, and mechanical properties of metallic glasses and will aid computer-driven materials design.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:first principle; force-field; glass transition; local order; phase transition; shear band; vibrational entropy
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Materials Science
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Johnson, William Lewis (advisor)
  • Goddard, William A., III (advisor)
Thesis Committee:
  • Johnson, William Lewis (chair)
  • Goddard, William A., III (co-chair)
  • Fultz, Brent T.
  • Ustundag, Ersan
  • Cross, Michael Clifford
Defense Date:21 May 2003
Author Email:hyon-jee (AT) caltech.edu
Record Number:CaltechETD:etd-05292003-165018
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05292003-165018
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2237
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:30 May 2003
Last Modified:29 May 2014 18:26

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[img] PDF (chapter_5.pdf) - Final Version
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