| 1. |
- Panda, Pritam Kumar, PhD Student, 1991-
(författare)
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GENOME2QUNOME : Interfacing Molecules with Nanomaterials
- 2023
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- The advent of technological furtherance in the biomedical sector and the renaissance of interdisciplinary science enable us to comprehend human lifestyle, and diseases at molecular and nanoscale levels. Lacking a shared theoretical foundation and terminological lexicon between various scientific domains might impede efforts to incorporate biological principles into nanoscience. In retrospect, it's possible to draw some instructive learnings from the fact that the development of contemporary nanoscience and biology was the consequence of the convergence of fields that had previously been kept separate. In this Ph.D. thesis, I have given the catchy moniker “GENOME2QUNOME” (an acronym for "Genetic organization of multicellular organisms and their enzymatic reaction 2 Quantum nanostructured materials for energy scavenging applications"), encompassing a combinatorial approach using computational methodologies in biophysics and nano/materials science. Structure-property correlations, a unifying paradigm based on understanding how nanomaterials behave and what qualities they exhibit at the molecular and nanoscale levels, are now widely acknowledged and are critical in the incorporation of bioinspired materials into nanoscience. Therefore, a unified framework have been elucidated in this thesis for the study of nanoscale materials ranging from 0D to 3D that may be useful in combining various strategies that characterize this interdisciplinary approach. This thesis is also a part of broader interdisciplinary research strategy aimed at depicting electronic transport in the nanoscale regime, elucidating interface mechanisms for contact electrification, and understanding the complex architectures of nanomaterials. The central hypothesis of this thesis is concentrated on the behavioral transition from the nanoscale regime to macromolecules, which is fascinating in real world scenario but theoretically challenging to bring it in reality or practice. To bridge this gap, I have made an attempt by integrating a wide range of computational methods, ranging from density functional theory (DFT) for systems with few atoms to classical dynamics dealing with billions of atoms.
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| 2. |
- Damas, Giane B.
(författare)
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Atomic Scale Modelling in Photoelectrocatalysis : Towards the Development of Efficient Materials for Solar Fuel Production
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Using sunlight to produce valuable chemicals has been pointed out as an interesting alternative to deal with the well-known environmental problem related to the use of fossil fuels for energy generation. Thus, it is crucial for this field the development of novel photocatalysts that could drive the uphill reactions with high efficiency while presenting low price and toxicity. In this context, conjugated polymers with a donor-acceptor architecture have shown good photoactivity for the hydrogen evolution reaction (HER) due to their advantageous properties, including a broad UV-Vis absorption spectrum and thermodynamic driving force to carry out the charge transfer processes. In this thesis, a series of fluorene- and benzothiadiazole-based polymers are evaluated by means of ab initio methods as potential candidates for photocatalytic HER. A set of small-molecules with well-defined molecular weight have also been considered for this application. In general, tailoring a chemical unit has enabled an improvement of the absorption capacity in benzo(triazole-thiadiazole)-based polymers and cyclopentadithiophene-based polymers, with a higher impact exhibited upon acceptor tailoring. On the other hand, all systems under investigation present favorable thermodynamics for proton reduction or hole removal by an appropriate sacrificial agent. In particular, it is demonstrated the active role played by nitrogen atoms from the acceptor units in the hydrogenation process, whose binding strength is significantly decreased in benzo(triazole-thiadiazole)-based polymers. Furthermore, the extension of the electron-hole separation has been assessed through the calculation of the exciton binding energies, which are diminished with an improvement in the donating ability on cyclopentadithiophene-based materials.In another approach to deal with the aforementioned problem, it has been considered the direct conversion of carbon dioxide into formic acid, an important chemical that finds applications in fuel cells, medicine and food industries. In this thesis, such electrocatalytic process has been investigated by using Sn-based electrodes and Ru-complexes. In the former case, a solid-state modelling approach based on slab geometries to model surface states has been employed to explore the reaction thermochemistry. The outcomes support the reaction mechanism where the carbon dioxide insertion into the Sn-OH bond is a thermodynamically favorable step prior to reduction, which has a redox potential in fair agreement with the measurements carried out by our collaborators. In a Ru-complex, the reaction mechanism is likely to follow the route with natural production of CO due to ligand release after the first reduction process, which is further protonated to originate the active species. In this case, the insertion occurs at the Ru-H bond to generate a carbon-bound species that is the intermediate in the formic acid production after the second protonation step. Finally, it has been studied the physical adsorption of carbon dioxide in metal-organic frameworks with a varying metallic center in a theoretical point of view.
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| 3. |
- Edin, Emil, 1987-
(författare)
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Computational Insights into Atomic Scale Wear Processes in Cemented Carbides
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As Ti-alloys become more and more utilized the need for efficient and robust manufacturing of Ti-alloy components increase in importance. Ti-alloys are more difficult to machine than e.g. steel, mainly due to their poor thermal conductivity leading to rapid tool wear. The atomic scale processes responsible for this wear is not well understood. Here the focus is turned to the effects of C diffusion out of the tools as a source of the observed wear. A combination of Density Functional Theory (DFT) making use of Harmonic Transition State Theory (HTST), classical Molecular Dynamics (MD) and kinetic Monte Carlo (kMC) is used to investigate C diffusion into and within experimentally observed WC/W interfaces that exists as a consequence of the C depletion. Further, tools are built and used to evaluate interface parameters for large sets of interfaces within the WC/W system to determine which are energetically preferred. The results from the DFT study show stable interfaces with large differences in activation energy between the two most prominent surfaces found in WC materials, namely the basal and prismatic surfaces. Within the WC/W interfaces the diffusion barriers are similar between the two. The classical MD simulations support the view of stable interfaces at the early stages of C depletion. As C is removed this picture shifts to one in which the diffusion barriers are substantially decreased and the difference between the basal and the prismatic interfaces vanish pointing to a process which starts out slow but accelerates as C is continually removed. From the kMC simulations the overall diffusion pre-factor and activation energy is estimated to be D0=1.8x10-8 m2/s and dE=1.24 eV for the investigated [10-10]-I/[100] interface, the kMC simulations also confirm previous results indicating that the diffusion is restricted to the interface region. The investigation and screening of properties for WC/W interfaces show a preference for the W terminated [10-10]-I/[110] and [0001]/[110] interface combinations based on the interfacial energy.
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| 4. |
- Triana, Carlos A, et al.
(författare)
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Modeling of Electronic Properties of Amorphous Oxides
- 2018
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Ingår i: Encyclopedia of Interfacial Chemistry. - : Elsevier. - 9780128097397 - 9780128098943 ; , s. 319-331
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Bokkapitel (refereegranskat)abstract
- Amorphous transition metal oxides (aTMOs) are used as multifunctional materials in many technological applications. A detailed understanding of the electronic density of states is a necessary prerequisite for modeling their functional properties. The electronic properties, however, are structure-dependent making the description of the electronic structure of disordered and amorphous materials challenging. Here we present a scheme based on obtaining atomic model structures from simulations of experimental X-ray-Absorption spectra, together with first principles electronic structure calculations. This approach provides a self-consistent framework to assess fundamental electronic processes in aTMOs and can be applied to the study of disordered and amorphous materials in general.
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