The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
Charles B. Musgrave - One of the best experts on this subject based on the ideXlab platform.
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Predicting Hydride Donor Strength via Quantum Chemical Calculations of Hydride Transfer Activation Free Energy
The journal of physical chemistry. B, 2018Co-Authors: Abdulaziz Alherz, Chern-hooi Lim, James T. Hynes, Charles B. MusgraveAbstract:We propose a method to approximate the kinetic properties of Hydride donor species by relating the nucleophilicity (N) of a Hydride to the activation free energy ΔG⧧ of its corresponding Hydride transfer reaction. N is a kinetic parameter related to the Hydride transfer rate constant that quantifies a nucleophilic hydridic species’ tendency to donate. Our method estimates N using quantum chemical calculations to compute ΔG⧧ for Hydride transfers from Hydride donors to CO2 in solution. A linear correlation for each class of Hydrides is then established between experimentally determined N values and the computationally predicted ΔG⧧; this relationship can then be used to predict nucleophilicity for different Hydride donors within each class. This approach is employed to determine N for four different classes of Hydride donors: two organic (carbon-based and benzimidazole-based) and two inorganic (boron and Silicon) Hydride classes. We argue that Silicon and boron Hydrides are driven by the formation of the m...
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Predicting Hydride Donor Strength via Quantum Chemical Calculations of Hydride Transfer Activation Free Energy
2017Co-Authors: Abdulaziz Alherz, Chern-hooi Lim, James T. Hynes, Charles B. MusgraveAbstract:We propose a method to approximate the kinetic properties of Hydride donor species by relating the nucleophilicity (N) of a Hydride to the activation free energy ΔG⧧ of its corresponding Hydride transfer reaction. N is a kinetic parameter related to the Hydride transfer rate constant that quantifies a nucleophilic hydridic species’ tendency to donate. Our method estimates N using quantum chemical calculations to compute ΔG⧧ for Hydride transfers from Hydride donors to CO2 in solution. A linear correlation for each class of Hydrides is then established between experimentally determined N values and the computationally predicted ΔG⧧; this relationship can then be used to predict nucleophilicity for different Hydride donors within each class. This approach is employed to determine N for four different classes of Hydride donors: two organic (carbon-based and benzimidazole-based) and two inorganic (boron and Silicon) Hydride classes. We argue that Silicon and boron Hydrides are driven by the formation of the more stable Si–O or B–O bond. In contrast, the carbon-based Hydrides considered herein are driven by the stability acquired upon rearomatization, a feature making these species of particular interest, because they both exhibit catalytic behavior and can be recycled
Linda J Broadbelt - One of the best experts on this subject based on the ideXlab platform.
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the role of multifunctional kinetics during early stage Silicon Hydride pyrolysis reactivity of si2h2 isomers with sih4 and si2h6
Journal of Physical Chemistry A, 2011Co-Authors: Andrew J Adamczyk, Linda J BroadbeltAbstract:Kinetic parameters for the dominant pathways during the addition of the four Si2H2 isomers, i.e., trans-HSiSiH, SiSiH2, Si(H)SiH, and Si(H2)Si, to monosilane, SiH4, and disilane, Si2H6, have been calculated using G3//B3LYP, statistical thermodynamics, conventional and variational transition state theory, and internal rotation corrections. The direct addition products of the multifunctional Si2H2 isomers were monofunctional substituted silylenes, hydrogen-bridged species, and silenes. During addition to monosilane and disilane, the SiSiH2 isomer was found to be most reactive over the temperature range of 800 to 1200 K. Revised parameters for the Evans−Polanyi correlation and a representative pre-exponential factor for multifunctional Silicon Hydride addition and elimination reaction families under pyrolysis conditions were regressed from the reactions in this study. This revised kinetic correlation was found to capture the activation energies and rate coefficients better than the current literature methods.
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kinetic correlations for h2 addition and elimination reaction mechanisms during Silicon Hydride pyrolysis
Physical Chemistry Chemical Physics, 2010Co-Authors: Andrew J Adamczyk, Mariefrancoise Reyniers, Guy Marin, Linda J BroadbeltAbstract:The mechanism of H2 addition and elimination reactions in selected Silicon Hydrides (SixHy, x = 1–10, y = 4–20) was modeled using quantum chemical calculations, statistical thermodynamics, transition state theory and transition state group additivity. Rate coefficients for 25 H2 addition reactions were calculated using G3//B3LYP. For nearly every reaction, the overall conversion exhibits two steps. In the addition direction, the reactants first meet to form an adduct which then converts into a saturated Silicon Hydride via homolytic H–H bond cleavage. Values for the single-event Arrhenius pre-exponential factor, A, and the activation energy, Ea, were calculated from the G3//B3LYP rate coefficients, and a group additivity scheme was developed to predict A and Ea. The values predicted by group additivity are more accurate than kinetic correlations currently used in the literature, which rely on representative A values and the Evans-Polanyi correlation. The factors that have the most pronounced effect on A and Ea were investigated, and stabilization of the divalent Silicon atom of the unsaturated Silicon Hydride with electron-donating substituents was found to influence kinetic parameters considerably. The rate coefficients for H2 addition reactions were found to correlate reasonably well with the difference in energy between the highest occupied molecular orbital of H2 (EHOMO) and the lowest unoccupied molecular orbital of the reactant silylene (ELUMO).
Abdulaziz Alherz - One of the best experts on this subject based on the ideXlab platform.
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Predicting Hydride Donor Strength via Quantum Chemical Calculations of Hydride Transfer Activation Free Energy
The journal of physical chemistry. B, 2018Co-Authors: Abdulaziz Alherz, Chern-hooi Lim, James T. Hynes, Charles B. MusgraveAbstract:We propose a method to approximate the kinetic properties of Hydride donor species by relating the nucleophilicity (N) of a Hydride to the activation free energy ΔG⧧ of its corresponding Hydride transfer reaction. N is a kinetic parameter related to the Hydride transfer rate constant that quantifies a nucleophilic hydridic species’ tendency to donate. Our method estimates N using quantum chemical calculations to compute ΔG⧧ for Hydride transfers from Hydride donors to CO2 in solution. A linear correlation for each class of Hydrides is then established between experimentally determined N values and the computationally predicted ΔG⧧; this relationship can then be used to predict nucleophilicity for different Hydride donors within each class. This approach is employed to determine N for four different classes of Hydride donors: two organic (carbon-based and benzimidazole-based) and two inorganic (boron and Silicon) Hydride classes. We argue that Silicon and boron Hydrides are driven by the formation of the m...
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Predicting Hydride Donor Strength via Quantum Chemical Calculations of Hydride Transfer Activation Free Energy
2017Co-Authors: Abdulaziz Alherz, Chern-hooi Lim, James T. Hynes, Charles B. MusgraveAbstract:We propose a method to approximate the kinetic properties of Hydride donor species by relating the nucleophilicity (N) of a Hydride to the activation free energy ΔG⧧ of its corresponding Hydride transfer reaction. N is a kinetic parameter related to the Hydride transfer rate constant that quantifies a nucleophilic hydridic species’ tendency to donate. Our method estimates N using quantum chemical calculations to compute ΔG⧧ for Hydride transfers from Hydride donors to CO2 in solution. A linear correlation for each class of Hydrides is then established between experimentally determined N values and the computationally predicted ΔG⧧; this relationship can then be used to predict nucleophilicity for different Hydride donors within each class. This approach is employed to determine N for four different classes of Hydride donors: two organic (carbon-based and benzimidazole-based) and two inorganic (boron and Silicon) Hydride classes. We argue that Silicon and boron Hydrides are driven by the formation of the more stable Si–O or B–O bond. In contrast, the carbon-based Hydrides considered herein are driven by the stability acquired upon rearomatization, a feature making these species of particular interest, because they both exhibit catalytic behavior and can be recycled
Donald G Truhlar - One of the best experts on this subject based on the ideXlab platform.
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nanodusty plasma chemistry a mechanistic and variational transition state theory study of the initial steps of silyl anion silane and silylene anion silane polymerization reactions
Physical Chemistry Chemical Physics, 2015Co-Authors: Prasenjit Seal, Donald G TruhlarAbstract:The growth of nanodusty particles, which is critical in plasma chemistry, physics, and engineering. The aim of the present work is to understand the detailed reaction mechanisms of early steps in this growth. The polymerization of neutral silane with the silylene or silyl anion, which eliminates molecular hydrogen with the formation of their higher homologues, governs the Silicon Hydride clustering in nanodusty plasma chemistry. The detailed mechanisms of these important polymerization reactions in terms of elementary reactions have not been proposed yet. In the present work, we investigated the initial steps of these polymerization reactions, i.e., the SiH4 + Si2H4−/Si2H5− reactions, and we propose a three-step mechanism, which is also applicable to the following polymerization steps. CM5 charges of all the Silicon-containing species were computed in order to analyze the character of the species in the proposed reaction mechanisms. We also calculated thermal rate constant of each step using multi-structural canonical variational transition state theory (MS-CVT) with the small-curvature tunneling (SCT) approximation, based on the minimum energy path computed using M08-HX/MG3S electronic structure method.
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large entropic effects on the thermochemistry of Silicon nanodusty plasma constituents
Journal of the American Chemical Society, 2014Co-Authors: Prasenjit Seal, Donald G TruhlarAbstract:Determination of the thermodynamic properties of reactor constituents is the first step in designing control strategies for plasma-mediated deposition processes and is also a key fundamental issue in physical chemistry. In this work, a recently proposed multistructural statistical thermodynamic method is used to show the importance of multiple structures and torsional anharmonicity in determining the thermodynamic properties of Silicon Hydride clusters, which are important both in plasmas and in thermally driven systems. It includes five different categories of Silicon Hydride clusters and radicals, including silanes, silyl radicals, and silenes. We employed a statistical mechanical approach, namely the recently developed multistructural (MS) anharmonicity method, in combination with density functional theory to calculate the partition functions, which in turn are used to estimate thermodynamic quantities, namely Gibbs free energy, enthalpy, entropy, and heat capacity, for all of the systems considered. T...
Mitsuo Koshi - One of the best experts on this subject based on the ideXlab platform.
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Reaction kinetics in Silicon chemical vapor deposition
Current Opinion in Solid State & Materials Science, 2002Co-Authors: Kenichi Tonokura, Mitsuo KoshiAbstract:Gas-phase reactions of simple Silicon Hydride species underlying many types of chemical vapor deposition processes for Silicon-based thin-film growth are reviewed in this paper. Mass spectrometry and laser-based spectroscopy are applied to identify gas-phase intermediates in thermal and hot-wire chemical vapor deposition processes. The mechanism of the thermal decomposition of silanes, including reactions that lead to the formation of hydrogenated Silicon clusters, is examined. The gas-phase chemical kinetic mechanism in hot-wire chemical vapor deposition is proposed to explain precursor molecules for the film growth.