Real-space electronic structure calculations for nanoscale systems

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dc.contributor Aalto-yliopisto fi
dc.contributor Aalto University en Torsti, Tuomas 2012-02-10T08:46:32Z 2012-02-10T08:46:32Z 2003-05-27
dc.identifier.isbn 951-22-6470-6
dc.identifier.issn 1455-1802
dc.description.abstract In this thesis, basic research focused on quantum systems relevant for the future nanotechnologies is presented. The research is modeling based on electronic structure calculations using the density-functional theory. For the solution of the ensuing Kohn-Sham equations, we have developed a new numerical scheme based on the Rayleigh quotient multigrid method. While an important part of the thesis is formed by software development for three-dimensional first-principles real-space electronic structure calculations, we use axially symmetric model systems in the study of nanostructures. This approximation reduces the computational demands and allows studies of rather large nanoscale systems encompassing hundreds or thousands of electrons. In addition, by restricting the geometry to the axial symmetry and resorting to jellium models, many random effects related to the detailed ionic structure are absent, and the relevant physics is easier to extract from the simulations. Nanowires can be considered as the ultimate conductors in which the atomistic confinement of electrons perpendicular to the wire and the atomistic length of the wire lead to quantum mechanical effects in cohesive and transport properties. The breaking process of a nanowire is studied using the ultimate jellium model, in which the positive background charge compensates in every point the electronic charge. Thereby, the shape of the narrowing constriction is free to vary so that the total energy is minimized. The prospect of molecular electronics is to use single molecules as circuit components. The electronic transport in atomic chains of a few Na atoms between cone-shaped leads is investigated in the thesis. Electrons residing in a Na island on the Cu(111) surface form a quantum dot system, in which the quantum mechanical confinement in all directions determines the electronic properties. We have developed a simple jellium model system which reproduces the characteristics of the confined electron states seen in scanning tunneling microscope experiments. en
dc.format.extent 49, [45]
dc.format.mimetype application/pdf
dc.language.iso en en
dc.publisher Helsinki University of Technology en
dc.publisher Teknillinen korkeakoulu fi
dc.relation.ispartofseries Dissertations / Laboratory of Physics, Helsinki University of Technology en
dc.relation.ispartofseries 121 en
dc.relation.haspart Heiskanen M., Torsti T., Puska M. J. and Nieminen R. M., 2001. Multigrid method for electronic structure calculations. Physical Review B 63, 245106, 8 pages. [article1.pdf] © 2001 American Physical Society. By permission.
dc.relation.haspart Torsti T., Heiskanen M., Puska M. J. and Nieminen R. M., 2003. MIKA: a multigrid-based program package for electronic structure calculations. International Journal of Quantum Chemistry 91, pages 171-176.
dc.relation.haspart Havu P., Torsti T., Puska M. J. and Nieminen R. M., 2002. Conductance oscillations in metallic nanocontacts. Physical Review B 66, 075401, 5 pages. [article3.pdf] © 2002 American Physical Society. By permission.
dc.relation.haspart Ogando E., Torsti T., Puska M. J. and Zabala N., 2003. Electronic resonance states in nanowires during the breaking process simulated with the ultimate jellium model. Physical Review B 67, 075417, 11 pages. [article4.pdf] © 2003 American Physical Society. By permission.
dc.relation.haspart Torsti T., Lindberg V., Puska M. J. and Hellsing B., 2002. Model study of adsorbed metallic quantum dots: Na on Cu(111). Physical Review B 66, 235420, 10 pages. [article5.pdf] © 2002 American Physical Society. By permission.
dc.subject.other Physics en
dc.title Real-space electronic structure calculations for nanoscale systems en
dc.type G5 Artikkeliväitöskirja fi
dc.description.version reviewed en
dc.contributor.department Department of Engineering Physics and Mathematics en
dc.contributor.department Teknillisen fysiikan ja matematiikan osasto fi
dc.subject.keyword electronic structure en
dc.subject.keyword density-functional theory en
dc.subject.keyword multigrid method en
dc.subject.keyword parallel computing en
dc.subject.keyword jellium models en
dc.subject.keyword nanowire en
dc.subject.keyword quantum dot en
dc.identifier.urn urn:nbn:fi:tkk-000504
dc.type.dcmitype text en
dc.type.ontasot Väitöskirja (artikkeli) fi
dc.type.ontasot Doctoral dissertation (article-based) en
dc.contributor.lab Laboratory of Physics en
dc.contributor.lab Fysiikan laboratorio fi

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