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dc.contributor.advisorGülseren, Oğuz
dc.contributor.authorMobaraki, Arash
dc.date.accessioned2019-10-03T10:51:21Z
dc.date.available2019-10-03T10:51:21Z
dc.date.copyright2019-09
dc.date.issued2019-09
dc.date.submitted2019-09-30
dc.identifier.urihttp://hdl.handle.net/11693/52519
dc.descriptionCataloged from PDF version of article.en_US
dc.descriptionThesis (Ph.D.): Bilkent University, Department of Physics, İhsan Doğramacı Bilkent University, 2019.en_US
dc.descriptionIncludes bibliographical references (leaves 94-110).en_US
dc.description.abstractA new era of nanodevice engineering has been started after fabricating graphene. This motivated vast number of researches for predicting, fabricating and utilizing 2D materials. Temperature dependent properties are essential for device applications. Although rigorous density functional theory based approaches are able to predict electronic and mechanical properties accurately, but they are mostly limited to zero temperature and ab initio based molecular dynamics are computationally very demanding. Classical molecular dynamics is a very powerful alternative, however its accuracy is basically depend on the interatomic potential used for describing the considered system and therefore constructing accurate force fields is always an open problem, especially for the emerging 2D materials with extra ordinary properties. Single-layer transition metal dichalcogenides (TMDs) are new class of 2D materials which are shown to be good candidates for thermoelectric applications, flexible electronic and optoelectronic devices. In order to investigate thermal properties of TMDs, Stillinger-Weber type potentials are developed using particle swarm optimization method. These potentials are validated by comparing the resulted phonon dispersion curves and thermal conductivities with available first principle and experimental results. In addition, for understanding the anharmonic effects imposed by the generated force fields the trends of the shifts of the optical phonon frequencies at 􀀀 point with variation in the temperature are compared with available experimental data. In all cases, optimized potentials generate results which are in agreement with the target data. In the second step, spectral energy density method together with phonon mode decomposition is used for obtaining temperature dependent phonon frequencies and lifetimes in entire Brillouin zone. The contribution of each phonon branch in thermal conductivity is predicted utilizing the obtained phonon lifetimes and group velocities within the framework of relaxation time approximation. Eventually, with the aim of constructing transferable potentials for describing 2D and bulk structures, a very fast and reliable optimization method is presented. Combining local and global optimization methods and utilizing the energy curves obtained from first principle method, novel Stillinger-Weber type potentials for graphene, silicene and group III nitrides are developed. The proposed approach provides a solid framework for parameter selection and investigating the role of each parameter in the resulted phonon dispersion curves.en_US
dc.description.statementofresponsibilityby Arash Mobarakien_US
dc.format.extentxiv, 110 leaves : charts (some color) ; 30 cm.en_US
dc.language.isoEnglishen_US
dc.rightsinfo:eu-repo/semantics/openAccessen_US
dc.subject2D materialsen_US
dc.subjectMolecular dynamicsen_US
dc.subjectInteratomic potentialsen_US
dc.subjectStillinger- Weber potentialen_US
dc.subjectSpectral energy density methoden_US
dc.subjectThermal conductivityen_US
dc.titleDevelopment of force fields for novel 2D materials for temperature dependent vibrational propertiesen_US
dc.title.alternativeYeni 2B malzemeler için etkileşim potensiyellerinin gelistirilmesi: sıcaklığa bağlı titreşim özelliklerien_US
dc.typeThesisen_US
dc.departmentDepartment of Physicsen_US
dc.publisherBilkent Universityen_US
dc.description.degreePh.D.en_US
dc.identifier.itemidB156255
dc.embargo.release2020-03-30


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