2026-09-19T16:53:48Zhttps://dspace.mit.edu/server/oai/requestoai:dspace.mit.edu:1721.1/323842022-01-13T07:54:36Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022
Ali S. Argon.
Demkowicz, Michael J. (Michael John), 1977-
Massachusetts Institute of Technology. Dept. of Mechanical Engineering.
Massachusetts Institute of Technology. Department of Mechanical Engineering
2006-03-29T18:39:38Z
2006-03-29T18:39:38Z
2005
2005
http://hdl.handle.net/1721.1/32384
61660392
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (p. 205-212).
Molecular dynamics simulation of amorphous silicon (a-Si) using the Stillinger- Weber potential reveals the existence of two distinct atomic environments: one solidlike and the other liquidlike. The mechanical behavior of a-Si when plastically deformed to large strain can be completely described by the mass fraction [phi] of liquidlike material in it. Specifically, samples with higher [phi] are more amenable to plastic flow, indicating that liquidlike atomic environments act as plasticity "carriers" in a-Si. When deformed under constant pressure, all a-Si samples converge to a unique value of [phi] characteristic of steady state flow. Discrete stress relaxations were found to be the source of low-temperature plastic flow in a-Si in deformation simulations by potential energy minimization. These relaxations are triggered when a local yielding criterion is satisfied in a small cluster of atoms. The atomic rearrangements accompanying discrete stress relaxations are describable as autocatalytic avalanches of unit shearing events. Every such unit event centers on a clearly identifiable change in bond length between the two split peaks of the second nearest neighbor shell in the radial distribution function (RDF) of bulk a-Si in steady-state low.
by Michael J. Demkowicz.
Ph.D.
213 p.
11049635 bytes
11063137 bytes
application/pdf
application/pdf
eng
Massachusetts Institute of Technology
M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.
http://dspace.mit.edu/handle/1721.1/7582
Mechanical Engineering.
Mechanisms of plastic deformation in amorphous silicon by atomistic simulation using the Stillinger-Weber potential
Thesis
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<Abstract>Molecular dynamics simulation of amorphous silicon (a-Si) using the Stillinger- Weber potential reveals the existence of two distinct atomic environments: one solidlike and the other liquidlike. The mechanical behavior of a-Si when plastically deformed to large strain can be completely described by the mass fraction [phi] of liquidlike material in it. Specifically, samples with higher [phi] are more amenable to plastic flow, indicating that liquidlike atomic environments act as plasticity "carriers" in a-Si. When deformed under constant pressure, all a-Si samples converge to a unique value of [phi] characteristic of steady state flow. Discrete stress relaxations were found to be the source of low-temperature plastic flow in a-Si in deformation simulations by potential energy minimization. These relaxations are triggered when a local yielding criterion is satisfied in a small cluster of atoms. The atomic rearrangements accompanying discrete stress relaxations are describable as autocatalytic avalanches of unit shearing events. Every such unit event centers on a clearly identifiable change in bond length between the two split peaks of the second nearest neighbor shell in the radial distribution function (RDF) of bulk a-Si in steady-state low.</Abstract>
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