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dc.contributor.advisorGülseren, Oğuzen_US
dc.contributor.authorOvalı, Rasim Volgaen_US
dc.date.accessioned2016-01-08T18:17:07Z
dc.date.available2016-01-08T18:17:07Z
dc.date.issued2010
dc.identifier.urihttp://hdl.handle.net/11693/15344
dc.descriptionAnkara : The Department of Physics and the Institute of Engineering and Science of Bilkent University, 2010.en_US
dc.descriptionThesis (Ph. D.) -- Bilkent University, 2010.en_US
dc.descriptionIncludes bibliographical references leaves 94-102.en_US
dc.description.abstractIn this thesis, the structures as well as mechanical and electronic properties of various boron nitride (BN) and graphene based two dimensional (2D) nano-structures are investigated in detail from rst-principle calculations using planewave pseudopotential method based on density functional theory. At the beginning of the thesis, essentials of the density functional theory (DFT) and a guidance for performing ab-initio calculations in the framework of DFT is presented. In addition, fundamentals about the exchange-correlation potential as well as approaches approximating it like local density approximation (LDA) and generalized gradient approximation (GGA) are discussed. Along with this thesis, rst of all, in order to understand the relation between the hexagonal boron nitride (h-BN) and cubic boron nitride (c-BN) and the growth of three dimensional (3D) BN structures, various defect structures introduce to BN monolayer, including point defects and especially highly curved defects such as n-fold rings, are investigated in detail. The calculated formation energies and structural analysis showed that 4-fold BN rings are the transient phase between h-BN to c-BN during c-BN nucleation. The charge density plots and density of states analysis further provide information about the electronic structure of these defect formations. Second of all, we have studied the formation of boron-nitride-carbon (BNC) ternary thin lms, so we observed the carbon nucleation in BN monolayer. These DFT based calculations show that carbon prefers the nitrogen site at rst step and the calculated defect energy indicates that carbon atoms tends to aggregate in BN hexagonal network, and hence increases the number of C-C bonds. BNC structures have magnetization of =1.0 B for odd number of carbon adsorption. Further substitution of carbon atoms into BN layer showed that carbon atomsform hexagonal rings instead of armchair or zigzag formations. Moreover, we calculated the vibrational modes of BN monolayer and BNC structures, and phonon density of states graphs are presented. The phonon frequencies intrinsic to C-C bond oscillations are observed, which is in good agreement with the experiment. Finally, point defects and ring formations on graphene are investigated in order to understand the Y-junction and kink formation in carbon nanotubes (CNTs). Pentagonal rings are the good candidates to initiate such 2D networks in CNTs. The curvature increases with increasing number of pentagonal rings. Moreover, interaction of sulphur atoms with graphene defects is studied. Final geometries and binding energies suggest that sulphur prefers to adsorb on defected regions, but it is not responsible for the formation of these structures or defects.en_US
dc.description.statementofresponsibilityOvalı, Rasim Volgaen_US
dc.format.extentxx, 102 leaves, illustrations, graphicsen_US
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subjectBoron nitrideen_US
dc.subjectdensity functional theoryen_US
dc.subjectab-initio,en_US
dc.subjectY-junctionen_US
dc.subjectn-fold ringsen_US
dc.subjecthighly curved defectsen_US
dc.subjectvacanciesen_US
dc.subjectpoint defectsen_US
dc.subjectsulphuren_US
dc.subjectcarbon nanotubesen_US
dc.subjectgrapheneen_US
dc.subject.lccTA418.9.N35 O83 2010en_US
dc.subject.lcshNanostructured materials.en_US
dc.subject.lcshGraphene.en_US
dc.subject.lcshBoron nitride.en_US
dc.subject.lcshNanotubes, Carbon.en_US
dc.titleBoron nitride and graphene 2D nanostructures from first-principlesen_US
dc.typeThesisen_US
dc.departmentDepartment of Physicsen_US
dc.publisherBilkent Universityen_US
dc.description.degreePh.D.en_US


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