Physical Sciences and Mathematics Commons^™

Development Of Computational Methods For Electronic Structural Characterization Of Strongly Correlated Materials: From Different Ab-Initio Perspectives, Uthpala K. Herath

Graduate Theses, Dissertations, and Problem Reports

The electronic correlations in materials drive a variety of fascinating phenomena from magnetism to metal-to-insulator transitions (MIT), which are due to the coupling between electron spin, charge, ionic displacements, and orbital ordering. Although Density Functional Theory (DFT) successfully describes the electronic structure of weakly interacting material systems, being a static mean-field approach, it fails to predict the properties of Strongly Correlated Materials (SCM) that include transition and rare earth metals where there is a prominent electron localization as in the case of d and f orbitals due to the nature of their spatial confinement.

Dynamical Mean Field Theory (DMFT) is …

D-Orbital Occupancy Of Transition Metal Oxides By X-Ray Absorption Near Edge Structure (Xanes), Eric Kurywczak

Seton Hall University Dissertations and Theses (ETDs)

XANES L₂ and L₃-edge X-Ray Absorption Near Edge Spectra (XANES) for 4d and 5d row transition metals (TM) oxides are assumed to be directly reflecting unoccupied d orbitals influenced by the local symmetry of the metal ion. XANES L₂- and L₃-edge data analysis through non-linear curve fitting allows for a unique, efficient look at the structural eccentricities of transition metal oxides. In this way it is possible to determine the oxidation state of a material as well as its site symmetry. We have used non-linear least-squares fitting across the near-edge region …

Computational Modeling Of Defect-Engineered Graphene Derivatives And Graphene-Polymer Nanocomposites, Asanka Weerasinghe

Doctoral Dissertations

Graphene has unique mechanical, electronic, and thermal properties, which enable a broad range of technological applications. For example, graphene flakes can be used as filler to enhance the properties of polymer-matrix nanocomposites and graphene derivatives, generated by defect engineering and chemical functionalization of single-layer graphene, have tunable properties that are very promising for engineering electronic and thermomechanical metamaterials. A fundamental understanding of the structure-property relationships that govern the function of such nanocomposites and graphene derivatives is required for designing and developing future graphene-based metamaterials. Toward this end, we have conducted a systematic study based on extensive molecular-dynamics simulations of mechanical …

Probing Quantum Transport In Three-Terminal Nanojunctions, Meghnath Jaishi

Dissertations, Master's Theses and Master's Reports

One-dimensional (1D) nanoscale systems—structures with the lateral dimensions ranging from 1 nm to 100 nm — have received significant research interest due to their unique structure-guided properties that promise functionalities far more superior than their bulk counterparts. The quantum confinement effect in 1D nanostructures provides us with a very powerful tool to tune their electrical, magnetic, optical and thermal properties and opens the gateway for their multifunctional usages in next-generation electronics. In particular, carbon nanotubes and semiconductor nanowires are found to offer tremendous opportunities to form the junction devices with controlled electronic and optoelectronic properties crucial to predictable device functions. …

Local Moments And Itinerant Electrons: Gaining New Insights Through Investigating Electronic And Dynamical Properties, Nicholas Steven Sirica

Doctoral Dissertations

Magnetic materials are often categorized in terms of either a purely local or a purely itinerant picture despite the fact that the vast majority actually fall within a spectrum that ranges between these two extremes. It is from such a starting point that this thesis aims at developing an understanding of how the complex interplay between local moments and itinerant electrons ultimately affects the electronic and dynamical properties. Such ideas are explored in greater detail using two materials as case studies: the chiral helimagnet Cr_1/3NbS₂ [Cr intercalated Niobium Disulfide] and YFe₂Ge₂ [Yttrium Iron Germanide] …

Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins

Doctoral Dissertations

Van der Waals (vdW) interactions influence a variety of mesoscale phenomena, such as surface adhesion, friction, and colloid stability, and play increasingly important roles as science seeks to design systems on increasingly smaller length scales. Using the full Lifshitz continuum formulation, this thesis investigates the effects of system materials, shapes, and configurations and presents open-source software to accurately calculate vdW interactions. In the Lifshitz formulation, the microscopic composition of a material is represented by its bulk dielectric response. Small changes in a dielectric response can result in substantial variations in the strength of vdW interactions. However, the relationship between these …

Understanding Electronic Structure And Transport Properties In Nanoscale Junctions, Kamal B. Dhungana

Dissertations, Master's Theses and Master's Reports - Open

Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder …