Author: Milena ShahuPublisher:
ISBN:
Category : Hydrocarbons
Languages : en
Pages : 240
Book Description
Experimental and Theoretical Chemical Dynamics of Small Hydrocarbon Molecules
Author: Milena ShahuPublisher:
ISBN:
Category : Hydrocarbons
Languages : en
Pages : 240
Book Description
Chemical Dynamics at Low Temperatures, Volume 88
Author: Victor A. BenderskiiPublisher: John Wiley & Sons
ISBN: 0470142006
Category : Science
Languages : en
Pages : 400
Book Description
The first unified treatment of experimental and theoreticaladvances in low-temperature chemistry Chemical Dynamics at LowTemperatures is a landmark publication. For the first time, thecumulative results of twenty years of experimental and theoreticalresearch into low-temperature chemistry have been collected andpresented in a unified treatment. The result is a text/referencethat both offers an overview of the subject and contains sufficientdetail to guide practicing researchers toward fertile ground forfuture research. Topics covered include: * Developmental history * Formulation of general problems and the main approximations usedto solve them * Specific features of tunneling chemical dynamics * One-dimensional tunneling in the path integral formalism * Special problems of two- and multidimensional tunneling * An extended presentation of pertinent experimental results
Generalizable Chemical Mechanism Extraction from Molecular Dynamics Simulations
Author: Vincent Jean Louis DufourPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Hydrocarbon pyrolysis is a process that is thought to occur in the interior of icy giant planets. This reaction would transform the methane contained in the interior of these planets into diamond through compression to pressure of several tens of gigapascals and heating to temperatures of several thousands of kelvins. Even if it is commonly admitted that this reaction occurs, the conditions under which it takes place are still debated. Many experiments and theoretical calculations gave disagreeing predictions; some experiments led to the observation of diamond from hydrocarbon pyrolysis in pressure as low as 10 GPa and temperatures between 2,000 and 3,000 K, whereas other experiments and theoretical predictions claimed that diamond cannot be produced by hydrocarbon pyrolysis below 100 GPa. Several explanations have been proposed to explain these discrepancies; however, there is no consensus yet and one of the main reasons is that the precise mechanism of hydrocarbon pyrolysis is not precisely known. A crude mechanism is that methane separates into dihydrogen and carbon-rich molecules, such as large hydrocarbons or solids. Nevertheless, this simplified mechanism leaves many topics unstudied: first, the kinetic of the reaction remains unknown. This limitation implies that researchers cannot guarantee that their experiments or simulations were run for a sufficient time to reach equilibrium. Another poorly understood topic is the role of pressure and temperature; it is generally assumed that diamond is more likely to be synthesized when pressure and temperature increases. But the exact conditions in which diamond is produced and the role of pressure and temperature has not been studied yet. Finally, the role of the hydrogen content has not been investigated; Le Chatelier's principle implies that the less hydrogen in the system, the larger the hydrocarbons will be, but it is unknown which hydrogen content induces diamond production. Therefore, there is a need for a detailed mechanism of hydrocarbon pyrolysis. Discovering the hydrocarbon pyrolysis mechanism through experiments is impractical because of the extreme conditions undergone and the short time scales involved. Recently, the rise of reactive force fields, such as ReaxFF, for Molecular Dynamics (MD) simulations allowed researchers to extract mechanisms from these MD simulations. Several methods have been developed for this extraction; however, the state-of-the-art methods display some limitations making them unsuitable for the study of hydrocarbon pyrolysis. First, these methods are only appropriate for the study of small molecules; since large molecules or solid particles appear in hydrocarbon pyrolysis, a framework that can both describe short and long molecules is needed. Second, the method cannot rely on theories such as Transition State Theory that were developed for gases. Hydrocarbon pyrolysis involves liquid and solid phases making these theories inappropriate. Eventually, the mechanisms are usually fitted to some specific conditions of temperature and pressure, but no extrapolation to new conditions have been performed. These extrapolations are especially important in low-reactivity conditions (low temperature and pressure) where MD simulations cannot reach equilibrium in reasonable computational time. In this dissertation, I am presenting the developments to mechanism extraction from MD simulations that made this method suitable for hydrocarbon pyrolysis. Mechanism extraction was performed on training MD simulations of hydrocarbon pyrolysis. From these simulations, the possible reactions that can occur in this system were extracted and their reaction rates estimated. From the list of reactions in the mechanism and their associated reaction rates, the evolution of hydrocarbon pyrolysis in different conditions was predicted by running Kinetic Monte Carlo (KMC) simulations that served here as an ordinary differential equation solver. This general framework was improved during my PhD. As a first contribution, reactions were described at the atomic scale, considering only the local structure around the reactive site and ignoring the rest of the molecules. This description differs from common mechanism where the reactions are described with the full molecules. This new description allowed me to describe both short and long molecules, condense the number of reactions to describe the system, predict the appearance of molecules unobserved in the initial MD simulations, transfer to the pyrolysis of new hydrocarbons, and extrapolate MD simulations to longer timescales. My second contribution was to perform temperature extrapolation on the extracted mechanism. This extrapolation enabled me to make accurate predictions of the evolution of different hydrocarbon pyrolysis in temperatures that were outside of the temperature range of the MD simulations that were used to extract the mechanism. I was able to make accurate predictions several hundred kelvins outside of this temperature range, run simulations on the microsecond-scale that would be too long to run for an MD simulation, and give insights to some experimental results of hydrocarbon pyrolysis. My final contribution involved the development of a model that predicts the size distribution of hydrocarbon at equilibrium in many different conditions from a simplified mechanism and random graph theory. This model can give quickly and accurately the equilibrium conditions that would otherwise need an MD simulation or a KMC simulation to be predicted.
Strained Hydrocarbons
Author: Helena DodziukPublisher: John Wiley & Sons
ISBN: 3527627146
Category : Science
Languages : en
Pages : 492
Book Description
In clearly structured chapters, this book covers the fascinating world of hydrocarbons, providing an insight into the fundamental principles of chemistry. The monograph covers modern aspects of the topic, such as carbon nanotubes, molecular flask inclusion, and fullerenes, with new synthetic procedures for the build up of the structural lattice included.
Modern Trends In Chemical Reaction Dynamics - Part Ii: Experiment And Theory
Author: Kopin LiuPublisher: World Scientific
ISBN: 9814482277
Category : Science
Languages : en
Pages : 539
Book Description
The field of chemical reaction dynamics has made tremendous progress during the last decade or so. This is due largely to the development of many new, state-of-the-art experimental and theoretical techniques during that period. It is beneficial to present these advances, both theoretical and experimental, in a review volume (Parts I and II). The primary purpose of this review volume is to provide graduate students and experts in the field with a rather detailed picture of the current status of advanced experimental and theoretical research in chemical reaction dynamics. All chapters in these two parts have been written by world-renowned experts active in such research.
Experimental and Theoretical Studies of Small Molecules in the Liquid State
Author: Thomas Clark StringfellowPublisher:
ISBN:
Category :
Languages : en
Pages : 412
Book Description
The Theory of Chemical Reaction Dynamics
Author: D.C. ClaryPublisher: Springer Science & Business Media
ISBN: 940094618X
Category : Science
Languages : en
Pages : 420
Book Description
The calculation of cross sections and rate constants for chemical reactions in the gas phase has long been a major problem in theoretical chemistry. The need for reliable and applicable theories in this field is evident when one considers the significant recent advances that have been made in developing experimental techniques, such as lasers and molecular beams, to probe the microscopic details of chemical reactions. For example, it is now becoming possible to measure cross sections for chemical reactions state selected in the vibrational rotational states of both reactants and products. Furthermore, in areas such as atmospheric, combustion and interstellar chemistry, there is an urgent need for reliable reaction rate constant data over a range of temperatures, and this information is often difficult to obtain in experiments. The classical trajectory method can be applied routinely to simple reactions, but this approach neglects important quantum mechanical effects such as tunnelling and resonances. For all these reasons, the quantum theory of reactive scattering is an area that has received considerable attention recently. This book describes the proceedings of a NATO Advanced Research Workshop held at CECAM, Orsay, France in June, 1985. The Workshop concentrated on a critical examination and discussion of the recent developments in the theory of chemical reaction dynamics, with particular emphasis on quantum theories. Several papers focus on exact theories for reactions.
Modelling the Dissociation Dynamics and Threshold Photoelectron Spectra of Small Halogenated Molecules
Author: Jonelle HarveyPublisher: Springer Science & Business Media
ISBN: 3319029762
Category : Science
Languages : en
Pages : 184
Book Description
Jonelle Harvey's book outlines two related experimental techniques, threshold photoelectron spectroscopy and threshold photoelectron photoion coincidence techniques, which are utilised to investigate small halogenated molecules. All the experiments were conducted at the vacuum ultraviolet beamline of the Swiss Light Source, a synchrotron photon source, which has the advantage over popular laser photon-sources of extreme ease of tunability. Three studies are presented which combine experimental and computational ab initio approaches: studying the fast dissociations of halogenated methanes in order to construct a self-consistent thermochemical network; investigating the fragmentations of fluoroethenes from timebombs, which break apart very slowly but explosively, to fast dissociators; and uncovering how vital conical interactions underpin both the results of photoelectron spectra and dissociation patterns. The details included in this thesis are useful for researchers working in the same field and those readers wishing to obtain a solid introduction into the types of systems encountered in threshold photoelectron photoion coincidence spectroscopy.
Spectroscopy, Dynamics and Molecular Theory of Carbon Plasmas and Vapors
Author: Laszlo NemesPublisher: World Scientific
ISBN: 9812837655
Category : Science
Languages : en
Pages : 536
Book Description
Ch. 1. Spectroscopy of carbon nanotube production processes / B.A. Cruden -- ch. 2. Spectroscopic studies on laser-produced carbon vapor / K. Sasaki -- ch. 3. Kinetic and diagnostic studies of carbon containing plasmas and vapors using laser absorption techniques / J. Ropcke, A. Rousseau and P.B. Davies -- ch. 4. Spectroscopy of carbon containing diatomic molecules / J.O. Hornkohl, L. Nemes and C. Parigger -- ch. 5. Optical emission spectroscopy of C[symbol] and C[symbol] molecules in laser ablation carbon plasma / N.A. Savastenko and N.V. Tarasenko -- ch. 6. Intra-cavity laser spectroscopy of carbon clusters / S. Raikov and L. Boufendi -- ch. 7. Dynamics of laser-ablated carbon plasma for thin film deposition : spectroscopic and imaging approach / R.K. Thareja and A.K. Sharma -- ch. 8. Laser spectroscopy of transient carbon species in the context of soot formation / V. Nevrly [und weitere] -- ch. 9. Developing new production and observation methods for various sized carbon nanomaterials from clusters to nanotubes / T. Sugai -- ch. 10. Potential model for molecular dynamics of carbon / A.M. Ito and H. Nakamura -- ch. 11. Electronic and molecular structures of small- and medium-sized carbon clusters / V. Parasuk -- ch. 12. Vibrational spectroscopy of linear carbon chains / C.-P. Chou [und weitere] -- ch. 13. Dynamics simulations of fullerene and SWCNT formation / S. Irle [und weitere] -- ch. 14. Mechanisms of carbon gasification reactions using electronic structure methods / J.F. Espinal, T.N. Truong and F. Mondragon
Modern Trends in Chemical Reaction Dynamics
Author: Xueming YangPublisher: World Scientific
ISBN: 9812389237
Category : Science
Languages : en
Pages : 539
Book Description
Annotation Provides a detailed picture of the current status of advanced experimental and theoretical research in chemical reaction dynamics. Topics include the Doppler-selected time-of-flight technique, multimass ion imaging, and photodissociation dynamics of free radicals.