Browsing by Author "Irle, S."

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Quantum Chemical Prediction of Pathways; and Rate Constants for Reactions of CO and CO(2) with Vacancy Defects on Graphite (0001) Surfaces
(2009-10-29)
Xu, S. C.
;
Irle, S.
;
Musaev, D. G.
;
Lin, M. C.
;
應用化學系分子科學碩博班
We present reaction pathways for adsorption of CO and CO(2) molecules in the vicinity of monovacancy defects on graphite (0001) based on B3LYP and dispersion-augmented density-functional tight-binding (DFTB-D) studies of the potential energy surfaces (PES) of these reactions. To model the graphite (0001) monovacancy defects, finite-size molecular model systems up to the size of dicircumcoronene (C(95)H(24)) were employed. We find that the CO molecule reacts readily with the monovacancy defects and partially "heals" the carbon hexagon network leading to the formation of a stable epoxide, whereas CO(2) oxidizes the defect via a dissociative adsorption pathway following CO elimination. We predict reaction rate constants in the temperature range between 300 and 3000 K using Rice-Ramsperger-Kassel-Marcus theory. Quantum chemical molecular dynamics simulations at 3000 K based on on-the-fly DFTB-D energies and gradients-support the results of our PES studies.
Quantum Chemical Prediction of Pathways; and Rate Constants for Reactions of CO and CO2 with Vacancy Defects on Graphite (0001) Surfaces
(2009-10-29)
Xu, S. C.
;
Irle, S.
;
Musaev, D. G.
;
Lin, M. C.
;
應用化學系分子科學碩博班
We present reaction pathways for adsorption of CO and CO2 molecules in the vicinity of monovacancy defects on graphite (0001) based on B3LYP and dispersion-augmented density-functional tight-binding (DFTB-D) studies of the potential energy surfaces (PES) of these reactions. To model the graphite (0001) monovacancy defects, finite-size molecular model systems up to the size of dicircumcoronene (C95H24) were employed. We find that the CO molecule reacts readily with the monovacancy defects and partially "heals" the carbon hexagon network leading to the formation of a stable epoxide, whereas CO2 oxidizes the defect via a dissociative adsorption pathway following CO elimination. We predict reaction rate constants in the temperature range between 300 and 3000 K using Rice-Ramsperger-Kassel-Marcus theory. Quantum chemical molecular dynamics simulations at 3000 K based on on-the-fly DFTB-D energies and gradients-support the results of our PES studies.
Quantum Chemical Prediction of Reaction Pathways and Rate Constants for Reactions of NO and NO(2) with Monovacancy Defects on Graphite (0001) Surfaces
(2010-05-13)
Xu, S. C.
;
Irle, S.
;
Lin, M. C.
;
應用化學系分子科學碩博班
;
Institute of Molecular science
We present reaction pathways for adsorption reactions of NO and NO(2) molecules in the vicinity of monovacancy defects on graphite (0001) based on quantum chemical potential energy surfaces (PESs) obtained by B3LYP and dispersion-augmented density-functional tight-binding (DFTB-D) methods. To model the graphite (0001) monovacancy defects, finite-size molecular model systems up to the size of dicircumcoronene (C(95)H(24)) were employed. We find that the reactions of NO(x) on the monodefective graphite surface are initiated by rapid association processes with negligible barriers, leading to nitridation and oxidation of the graphite surface, and eventually producing gaseous CO(x), NO, and CN species leaving from an even more defective graphite surface. On the basis of the computed reaction pathways, we predict reaction rate constants in the temperature range between 300 and 3000 K using Rice-Ramsperger-Kassel-Marcus theory. High-temperature quantum chemical molecular dynamics simulations at 3000 K based on on-the-fly DFTB-D energies and gradients support the results of our PES studies.
Quantum Chemical Prediction of Reaction Pathways and Rate Constants for Reactions of NO and NO2 with Monovacancy Defects on Graphite (0001) Surfaces
(2010-05-13)
Xu, S. C.
;
Irle, S.
;
Lin, M. C.
;
應用化學系
;
Department of Applied Chemistry
We present reaction pathways for adsorption reactions of NO and NO2 molecules in the vicinity of monovacancy defects on graphite (0001) based on quantum chemical potential energy surfaces (PESs) obtained by B3LYP and dispersion-augmented density-functional tight-binding (DFTB-D) methods. To model the graphite (0001) monovacancy defects, finite-size molecular model systems up to the size of dicircumcoronene (C95H24) were employed. We find that the reactions of NOx on the monodefective graphite surface are initiated by rapid association processes with negligible barriers, leading to nitridation and oxidation of the graphite surface, and eventually producing gaseous COx, NO, and CN species leaving from an even more defective graphite surface. On the basis of the computed reaction pathways, we predict reaction rate constants in the temperature range between 300 and 3000 K using Rice-Ramsperger-Kassel-Marcus theory. High-temperature quantum chemical molecular dynamics simulations at 3000 K based on on-the-fly DFTB-D energies and gradients support the results of our PES studies.
Relative Isomer Abundance of Fullerenes and Carbon Nanotubes Correlates with Kinetic Stability
(2011-10-20)
Fedorov, A. S.
;
Fedorov, D. A.
;
Kuzubov, A. A.
;
Avramov, P. V.
;
Nishimura, Y.
A methodology to evaluate the kinetic stability of carbon nanostructures is presented based on the assumption of the independent and random nature of thermal vibrations. The kinetic stability is directly correlated to the cleavage probability for the weakest bond of a given nanostructure. The application of the presented method to fullerenes and carbon nanotubes yields clear correlation to their experimentally observed relative isomer abundances. The general and simple formulation of the method ensures its applicability to other nanostructures for which formation is controlled by kinetic factors.