Atomistics of defect nucleation and mobility : dislocations and twinning

Multiscale materials modeling has emerged in recent years as a significant concept and the only viable approach to understand the mechanical response of materials by linking modeling research at different length scales and time scales, including quantum mechanics, atomistics modeling, mesoscale modeling and continuum modeling together. The role that atomistic modeling plays is important and indispensable in that it can generate understanding of the physics and pass this mechanistic understanding as well as important parameters to higher level simulations. This thesis presents theories and simulations of defect nucleation and mobility in BCC transition metal molybdenum using atomistic methods, with the two primary defects of interest being dislocations and deformation twinning, and emphasis on the atomistic mechanisms and measures. The contributions presented in the thesis may be regarded as advances in both methods development and mechanistic understanding of dislocation mobility and twinning nucleation. For atomistic studies of dislocations in a simulation cell of finite size, new methods have been derived to (1) calculate the atomic displacement field under PBC and generate atomic dislocation configuration from this displacement field; (2) quantify artificial image effect for a dislocation moving within the periodic cell and optimize geometry of simulation cell to minimize such effects. These methodological breakthroughs serve as the basis for atomistic studies of dislocations and are used repeatedly in this thesis. To understand the complex plasticity behavior of BCC metal molybdenum, we need to first understand the most fundamental problem of core structure

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Nuclear Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Chang, Jinpeng, 1974-

Advisor dc:contributor.advisor

• Sidney Yip.

• Nuclear Engineering.

Statement dc:rights

• 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.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/16601

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/16601