{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/49547"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/49547","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Real time density functional simulations of quantum scale conductance","abstract":"We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory (TDDFT). This is in contrast with the more common steady-state nonequilibrium Green's function (NEGF) method. We start by examining quantum scale conductance methods in both the steady state and real-time formulations followed by a review of computational quantum chemistry methods. We then develop the real-time density functional theory and numerical solution techniques and use them to examine transport in a simple trans-polyacetylene wire. The remaining chapters are devoted to examining real-time transport behavior of various systems and model chemistries. Open-shell calculation of the polyacetylene wire reveal that, in agreement with various correlated model calculations, charge and spin behave as separate quasiparticles with different rates of transport. However, the transport of charge, and especially spin are highly dependent upon the amount of exact exchange included in the approximate exchange-correlation energy functional. This functional dependence is further illustrated when we demonstrate that the conductance gap of a device imperfectly coupled to wires varies based upon the non-local exchange and correlation. We also study the dynamic transport behavior of benzene-1,4-dithiol (BDT) coupled to gold leads and find that both the transient current and device charge density fluctuate with time,. This suggests that the steady-state assumption of the NEGF method may not be accurate.","abstract_html":"We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory (TDDFT). This is in contrast with the more common steady-state nonequilibrium Green's function (NEGF) method. We start by examining quantum scale conductance methods in both the steady state and real-time formulations followed by a review of computational quantum chemistry methods. We then develop the real-time density functional theory and numerical solution techniques and use them to examine transport in a simple trans-polyacetylene wire. The remaining chapters are devoted to examining real-time transport behavior of various systems and model chemistries. Open-shell calculation of the polyacetylene wire reveal that, in agreement with various correlated model calculations, charge and spin behave as separate quasiparticles with different rates of transport. However, the transport of charge, and especially spin are highly dependent upon the amount of exact exchange included in the approximate exchange-correlation energy functional. This functional dependence is further illustrated when we demonstrate that the conductance gap of a device imperfectly coupled to wires varies based upon the non-local exchange and correlation. We also study the dynamic transport behavior of benzene-1,4-dithiol (BDT) coupled to gold leads and find that both the transient current and device charge density fluctuate with time,. This suggests that the steady-state assumption of the NEGF method may not be accurate.","abstract_has_math":false,"creators":["Evans, Jeremy Scott"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Dept. of Chemistry.","school":null,"contributors":[],"advisors":["Troy Van Voorhis."],"committee_chairs":[],"committee_members":[],"year":2009,"date_issued":"2009","date_published":"2009","updated_at":"2026-07-22T22:22:01Z","subjects":["Chemistry."],"languages":["eng"],"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."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/49547","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Troy Van Voorhis."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. Dept. of Chemistry."]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Massachusetts Institute of Technology. Dept. of Chemistry."]},{"key":"dc:creator","label":"Author","values":["Evans, Jeremy Scott"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2009-11-06T14:50:23Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2009-11-06T14:50:23Z"]},{"key":"dc:date.issued","label":"Date","values":["2009"]},{"key":"dc:publisher","label":"Institution","values":["Massachusetts Institute of Technology"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry."]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["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."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/1721.1/49547"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.","This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.","Includes bibliographical references (p. 141-158)."]},{"key":"dc:description.abstract","label":"Abstract","values":["We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory (TDDFT). This is in contrast with the more common steady-state nonequilibrium Green's function (NEGF) method. We start by examining quantum scale conductance methods in both the steady state and real-time formulations followed by a review of computational quantum chemistry methods. We then develop the real-time density functional theory and numerical solution techniques and use them to examine transport in a simple trans-polyacetylene wire. The remaining chapters are devoted to examining real-time transport behavior of various systems and model chemistries. Open-shell calculation of the polyacetylene wire reveal that, in agreement with various correlated model calculations, charge and spin behave as separate quasiparticles with different rates of transport. However, the transport of charge, and especially spin are highly dependent upon the amount of exact exchange included in the approximate exchange-correlation energy functional. This functional dependence is further illustrated when we demonstrate that the conductance gap of a device imperfectly coupled to wires varies based upon the non-local exchange and correlation. We also study the dynamic transport behavior of benzene-1,4-dithiol (BDT) coupled to gold leads and find that both the transient current and device charge density fluctuate with time,. This suggests that the steady-state assumption of the NEGF method may not be accurate."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Real time density functional simulations of quantum scale conductance"]}]}],"canonical_facts":{"dc:contributor.advisor":["Troy Van Voorhis."],"dc:contributor.department":["Massachusetts Institute of Technology. Dept. of Chemistry."],"dc:contributor.other":["Massachusetts Institute of Technology. Dept. of Chemistry."],"dc:creator":["Evans, Jeremy Scott"],"dc:date.accessioned":["2009-11-06T14:50:23Z"],"dc:date.available":["2009-11-06T14:50:23Z"],"dc:date.issued":["2009"],"dc:description":["Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2009.","This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.","Includes bibliographical references (p. 141-158)."],"dc:description.abstract":["We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory (TDDFT). This is in contrast with the more common steady-state nonequilibrium Green's function (NEGF) method. We start by examining quantum scale conductance methods in both the steady state and real-time formulations followed by a review of computational quantum chemistry methods. We then develop the real-time density functional theory and numerical solution techniques and use them to examine transport in a simple trans-polyacetylene wire. The remaining chapters are devoted to examining real-time transport behavior of various systems and model chemistries. Open-shell calculation of the polyacetylene wire reveal that, in agreement with various correlated model calculations, charge and spin behave as separate quasiparticles with different rates of transport. However, the transport of charge, and especially spin are highly dependent upon the amount of exact exchange included in the approximate exchange-correlation energy functional. This functional dependence is further illustrated when we demonstrate that the conductance gap of a device imperfectly coupled to wires varies based upon the non-local exchange and correlation. We also study the dynamic transport behavior of benzene-1,4-dithiol (BDT) coupled to gold leads and find that both the transient current and device charge density fluctuate with time,. This suggests that the steady-state assumption of the NEGF method may not be accurate."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["http://hdl.handle.net/1721.1/49547"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"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."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Chemistry."],"dc:title":["Real time density functional simulations of quantum scale conductance"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:22:01Z"}