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New perspectives on ab initio calculation and physical insights gained through linkage to continuum theories

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dc.contributor.advisor Tomás A. Arias and John D. Joannopoulos. en_US
dc.contributor.author Ismail-Beigi, Sohrab, 1971- en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Physics. en_US
dc.date.accessioned 2007-11-16T14:36:31Z
dc.date.available 2007-11-16T14:36:31Z
dc.date.copyright 2000 en_US
dc.date.issued 2000 en_US
dc.identifier.uri http://hdl.handle.net/1721.1/39637
dc.description Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Physics, 2000. en_US
dc.description Includes bibliographical references (p. 159-165). en_US
dc.description.abstract We explore the use of ab initio, density-functional methods for the study of large-scale materials problems. Three examples are presented: (i) the interplay of surface and edge reconstructions in long silicon nanowires, where we examine the effects on electrical and mechanical properties; (ii) the calculation of solvation effects based on ab initio dielectric models, where we derive the dielectric treatment as a coarse-grained molecular description, apply our method to the hydrolysis reaction of methylene chloride, and examine simplifications to our ab initio method; and (iii) the study of screw dislocation cores in bcc molybdenum and tantalum, where we find core structures contrary to those commonly accepted and barriers to dislocation motion in better agreement with experiment. Methodologically, we present a new matrix-based, algebraic formalism for ab initio calculations which modularizes and isolates the roles played by the basis set, the energy functional, the algorithm used to achieve self-consistency, and the computational kernels. Development and implementation of new techniques amounts to derivation and transcription of algebraic expressions. Modularizing the computational kernels yields portable codes that are easily optimized and parallelized, and we present highly efficient kernels for scalar, shared, and distributed memory computers. We conclude with an analytical study of the spatial locality of the single-particle density matrix in solid-state systems. This locality reflects the localization of electronic states and is essential for real-space and O(N) methods. We derive new behavior for this spatial range contrary to previous proposals, and we verify our findings in model semiconductors, insulators, and metals. en_US
dc.description.statementofresponsibility by Sohrab Ismail-Beigi. en_US
dc.format.extent 165 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
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. en_US
dc.rights.uri http://dspace.mit.edu/handle/1721.1/7582
dc.subject Physics. en_US
dc.title New perspectives on ab initio calculation and physical insights gained through linkage to continuum theories en_US
dc.title.alternative Ab initio calculation and physical insights gained through linkage to continuum theories en_US
dc.type Thesis en_US
dc.description.degree Ph.D. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Physics. en_US
dc.identifier.oclc 47839618 en_US


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