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Physics

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Density functional theory

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Experimental And Computational Studies Of Functionalized Carbon Nanotubes For Use In Energy Storage Devices And Membranes, Emine S. Karaman Dec 2021

Experimental And Computational Studies Of Functionalized Carbon Nanotubes For Use In Energy Storage Devices And Membranes, Emine S. Karaman

Dissertations

Electrolytes with good interfacial stability are a crucial component of any electrochemical device. The development of novel gel polymer electrolytes (GEs) with good interface stability and better manufacturability is important for the development of the next generation electrochemical devices. Gel electrolytes are hybrid electrolyte materials, combining benefits of both liquid and solid systems. Compared with liquid and solid electrolytes, GEs open new design opportunities and do not require rigorous encapsulation methods. In this dissertation, studies on functionalized carbon nanotubes (fCNTs) and graphene oxide (GO) doped polyvinyl alcohol (PVA) based gel electrolytes (GEs) are reported. The ionic conductivity and mechanical strength …


First-Principles Density Functional Theory Studies On Perovskite Materials, Aneer Lamichhane May 2021

First-Principles Density Functional Theory Studies On Perovskite Materials, Aneer Lamichhane

Dissertations

Perovskites are a family of materials with a diverse combination of different elements. As a consequence, they exhibit numerous functionalities such as pyroelectric, piezoelectric, ferroelectric, and ferromagnetic with applications in photovoltaic cells, LEDs, superconductivity, colossal magneto-resistance, and topological insulators. After 2009, perovskites have gained notoriety as suitable materials for solar cells and alternative candidates to silicon-based conventional solar cells. Generally, oxide perovskites exhibit good dielectric properties, halide perovskites display good photonic qualities, and chalcogenide perovskites are used in applications in solid-state lighting, sensing, and energy harvesting. In this dissertation, various types of perovskites ranging from oxide to halide are investigated …


Microstructure, Vacancies And Voids In Hydrogenated Amorphous Silicon, Rajendra Timilsina Dec 2012

Microstructure, Vacancies And Voids In Hydrogenated Amorphous Silicon, Rajendra Timilsina

Dissertations

This dissertation presents a theoretical and computational study of microstructure, vacancies and voids in hydrogenated amorphous silicon (a-Si:H). The microstructure consists of all possible silicon-hydrogen bonding configurations such as SiH, SiH2, SiH3 and SiH4. However, it is highly dominated (approximately 75% or even more) by monohydride (SiH) configurations. Furthermore, the hydrogen atoms locate in both clustered and diluted phases; as a result, the distribution becomes highly inhomogeneous. Approximately 5% of hydrogen atoms reside in a form of isolated monohydrides at the lower (7 at.%) concentration whereas such configurations do not appear at the higher concentrations …