Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 14 of 14 for “"Reaction Barriers"”.
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Quantum Perspectives on Physical and Inorganic Chemistry
… The ccCA was found to reproduce classical reaction barriers with chemical accuracy, outperforming all DFT, ab initio, and composite methods benchmarked.
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Density Functional Theory Calculations Complement Mass Spectrometry Experiments in the Investigation of Biomass Fast Pyrolysis and Ion-Molecule Reaction Mechanisms
… since the 1970s, current models and hypothesized reaction networks fail to explain the product distribution even for a simple model compound, the cellulose dimer, cellobiose. A novel approach of using mass spectrometry to instantly characterize fast pyrolysis vapors allows for identification of …
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Reactions of Halogenated Ethylenes on the α-Cr₂O₃ (101̅2) Surface
The thermally induced reaction of halogenated ethylenes on the α-Cr₂O₃ (101̅2) single crystal surface results in the formation of gas phase hydrocarbons including acetylene, ethylene, butadiene, and dihydrogen, and deposition of surface chlorine adatoms. No surface carbon or combustion products are …
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A computational study of the structure, bonding, and thermochemical properties of primary Ozonides derived from substituted Phenol and Thiophenol
… and hydroxythiophenol ozonolysis yields reaction barriers of 56.8, 11.2 and 10.4 kcal/mol for the formation of the most stable POZs, respectively. The lowest energy POZs for chlorophenol, dihydroxybenzene and hydroxythiophenol are located at 19.1, 22.1 and 19.4 kcal/mol below the …
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Theoretical exploration of char formation during lignin pyrolysis
… to study the energetics and mechanisms of reactions involved in lignin char formation.<br/> <br/>In Chapter 1, the background for the project is given, highlighting the global climate and energy crises, as well as providing an overview of biomass, biofuels, and biomass thermochemical …
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First Principles Study Of Tribopolymerization On Conductive Material Surfaces
… following stress confined surface catalytic reactions to form tribopolymers, which are usually insulating and sticky. Experimental results only justify those tribopolymers to be hydrocarbon chains, but detailed composition and formation mechanism remain unclear. Here, we perform theoretical …
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Approximations to Matsubara Dynamics for Vibrational Spectra
… introduces artefacts into the calculation, near reaction barriers, but the resulting errors are found to be minor. With classical and path-integral simulations of isotopically substituted systems we investigate the role of dynamical vibrational couplings in condensed-phase water. We show that the …
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Rational Design of Supported Metal Catalysts for Carbonyl Reduction During Biomass Upgrading
… of hydrogenation of acetone. The apparent reaction orders of hydrogen and acetone, apparent activation energies, and observed kinetic isotope effects over a large range of temperatures and concentrations (compound partial pressures) are reported in this document. Generally speaking, the …
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Wannier Functions and Their Role in Improving Density Functional Approximations
… some properties such as dissociation energies, reaction barriers, and band gaps. These deficiencies can be traced to delocalization error in density functional approximations. In finite systems, delocalization error can be attributed to the incorrect treatment of fractional electron charge …
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Analyzing Electronic Correlation Effects in Molecules and Semiconductor Point Defects from First Principles Beyond Density Functional Theory
… of bandgaps in solids, underestimated reaction barriers in molecules, and incorrect dissociation curves. The second area is the case where the ground and/or excited states are described by multiconfigurational wavefunctions rather than a single Slater determinant. Chapter 1 of the …
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Accurate Calculations of Molecular Properties with Explicitly Correlated Methods
… chemical reactivity. The reference data include reaction barrier heights, electronic reaction energies, atomization energies, and enthalpies of formation from the following sources: (1) the DBH24/08 database of 22 reaction barriers (Truhlar et al., J. Chem. Theory Comput., 2007, 3, 569.), (2) the …
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Towards sustainable heterogenous catalysis in molecular solar thermal energy storage (MOST) systems
… doctoral thesis focuses on triggering the back-reaction in MOlecular Solar Thermal (MOST) energy storage systems using heterogenous catalysts. The MOST system consists of a pair of organic switchable molecules which can capture solar radiation, can store the energy within its chemical bonds and …
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Understanding Heterogenous Catalysis on Zeolites and Manganese Oxides
… aiming to understand heterogenous catalytic reactions over zeolites and two different octahedral manganese oxides. <br/><br/>To further understand shape-selectivity in zeolites, a complete free energy profile for different chain-sized alkynes in Cu-SSZ-13 was studied, using DFT and biased MD …
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Assessment of Reactivity Descriptors for the Study of Chemical Reactions
… to study molecular systems and chemical reactions. In this light, ab initio many body techniques enable us, without any experimental input, to compute molecular energetics and a whole range of chemical properties. A twofold classification can be made, separating wave function based …