Complex Gas Phase Reactions Research Articles

Reconciling Accuracy and Feasibility for Barrierless Reaction Steps by the PCS/DDCI/MC-PDFT Protocol: Methane and Ethylene Dissociations as Case Studies.

Several enhancements have been introduced into state-of-the-art computational protocols for the treatment of barrierless reaction steps in the framework of variable reaction coordinate variational transition state theory. The first step is the synergistic integration of the Iterative Difference Dedicated Configuration Interaction (I-DDCI) and Pisa Composite Scheme, which defines a reduced cost, yet very accurate, computational workflow. This approach provides a near black box tool for obtaining 1D reference potentials. Then, a general strategy has been devised for tuning the level of theory used in Monte Carlo (MC) sampling, employing Multiconfiguration Pair Density Functional Theory (MC-PDFT) with dynamically adjusted Hartree-Fock exchange. Concurrently, partial geometry optimizations during the MC simulations account for the coupling between the reaction coordinates and conserved modes. The protocol closely approaches full size consistency and yields highly accurate results, with several test computations suggesting rapid convergence of the I-DDCI correction with the basis set dimensions. The capabilities of the new platform are illustrated by two case studies (the hydrogen dissociation from CH4 and C2H4), which highlight its flexibility in handling different carbon hybridizations (sp3 and sp2). The remarkable accuracy of the computed rate constants confirms the robustness of the proposed method. Together with their intrinsic interest, these results pave the way for systematic investigations of complex gas-phase reactions through a reliable, user-friendly tool accessible to specialists and nonspecialists alike.

New Instrument for Time-Resolved OH and HO2 Quantification in High-Pressure Laboratory Kinetics Studies.

We have constructed a new time-resolved high-pressure fluorescence assay by gas expansion (HP-FAGE) apparatus, optimized for the detection of OH and HO2 radicals in complex gas-phase reactions. The new instrument fills a gap in the existing experimental toolkit for chemical kinetics by enabling the quantification of two key reactive species with microsecond time resolution from high-pressure sources, which was previously not attainable. The HP-FAGE is interfaced with a flow reactor, designed for pressures up to 100 bar and temperatures up to 1000 K, in which reactions are initiated by laser photolysis of radical precursors at repetition rates of 1-10 Hz. The HP-FAGE samples gas out of the reactor into a miniature FAGE chamber, where OH is detected by resonant laser-induced fluorescence using a time-delayed probe laser pulse. HO2 is converted to OH via reaction with NO and then detected by OH fluorescence. The novel FAGE design places the probe region very close to the gas expansion, minimizing the transport time of sampled molecules and resulting in time resolution better than 20 μs for both OH and HO2. We calibrate the sensitivity of HP-FAGE, validate its performance with measurements of well-known reaction kinetics (OH + CH4, OH + OH, OH + HO2, and HO2 + HO2), and discuss prospects for its future use.

Improved microcanonical instanton theory.

Canonical (thermal) instanton theory is now routinely applicable to complex gas-phase reactions and allows for the accurate description of tunnelling in highly non-separable systems. Microcanonical instanton theory is by contrast far less well established. Here, we demonstrate that the best established microcanonical theory [S. Chapman, B. C. Garrett and W. H. Miller, J. Chem. Phys., 1975, 63, 2710-2716], fails to accurately describe the deep-tunnelling regime for systems where the frequencies of the orthogonal modes change rapidly along the instanton path. By taking a first principles approach to the derivation of microcanonical instanton theory, we obtain an improved method, which accurately recovers the thermal instanton rate when integrated over energy. The resulting theory also correctly recovers the separable limit and can be thought of as an instanton generalisation of Rice-Ramsperger-Kassel-Marcus (RRKM) theory. When combined with the density-of-states approach [W. Fang, P. Winter and J. O. Richardson, J. Chem. Theory Comput., 2021, 17, 40-55], this new method can be straightforwardly applied to real molecular systems.

Dynamics Insight into Isomerization and Dissociation of Hot Criegee Intermediate CH3CHOO.

We study the isomerization and dissociation of syn-CH3CHOO with high internal energies by combining electronic structure calculations, ab initio molecular dynamics, and RRKM microcanonical variational transition-state theories. The results show a striking effect of the internal energy on the reaction fate of syn-CH3CHOO. With lower internal energies, syn-CH3CHOO prefers isomerizing to vinyl hydroperoxide, which then produces hydroxyl radical. As the available internal energy increases, the O-elimination channel becomes more competitive and eventually the dominant channel. A third channel leading to methyl dioxirane is found to be less competitive than the former two. However, this channel is highly exothermic and produces greenhouse gases CH4 and CO2; thus, further investigation is needed to quantify its potential impact on the atmosphere. The present study provides new insight on clarifying the unimolecular reaction fate of hot syn-CH3CHOO and theoretical solutions for revealing the impact of internal energy on the complex gas phase reactions.

Global minimum profile error (GMPE) - a least-squares-based approach for extracting macroscopic rate coefficients for complex gas-phase chemical reactions.

Master equation/Rice-Ramsperger-Kassel-Marcus (ME/RRKM) has shown to be a powerful framework for modeling kinetic and dynamic behaviors of a complex gas-phase chemical system on a complicated multiple-species and multiple-channel potential energy surface (PES) for a wide range of temperatures and pressures. Derived from the ME time-resolved species profiles, the macroscopic or phenomenological rate coefficients are essential for many reaction engineering applications including those in combustion and atmospheric chemistry. Therefore, in this study, a least-squares-based approach named Global Minimum Profile Error (GMPE) was proposed and implemented in the MultiSpecies-MultiChannel (MSMC) code (Int. J. Chem. Kinet., 2015, 47, 564) to extract macroscopic rate coefficients for such a complicated system. The capability and limitations of the new approach were discussed in several well-defined test cases.

Preparation of mullite whisker skeleton porous ceramic

Sillimanite whisker skeleton porous ceramic was firstly prepared by an appropriate firing process from kaolinite and ammonium hexafluoroaluminate (AHA) as raw materials, then mullite whisker and corundum were produced by firing the sillimanite whisker skeleton at 1400°C. Effect of firing system on the sillimanite whisker skeleton formation was examined in detail. A series of complex gas phase reactions between the kaolinite and ammonium hexafluoroaluminate (AHA) caused the sillimanite whisker skeleton formation in the ceramic body. The experimental results show that one-step firing process with fast heating rate leads to the hexagonal shaped α-Al2O3 platelet forming, but the slow heating rate or two-step firing processes can completely cause the whisker skeleton structure generation.

ChemInform Abstract: Hot Wire Chemical Vapor Deposition Chemistry in the Gas Phase and on the Catalyst Surface with Organosilicon Compounds

AbstractReview: 45 refs.

Hot wire chemical vapor deposition chemistry in the gas phase and on the catalyst surface with organosilicon compounds.

CONSPECTUS: Hot wire chemical vapor deposition (HWCVD), also referred to as catalytic CVD (Cat-CVD), has been used to produce Si-containing thin films, nanomaterials, and functional polymer coatings that have found wide applications in microelectronic and photovoltaic devices, in automobiles, and in biotechnology. The success of HWCVD is largely due to its various advantages, including high deposition rate, low substrate temperatures, lack of plasma-induced damage, and large-area uniformity. Film growth in HWCVD is induced by reactive species generated from primary decomposition on the metal wire or from secondary reactions in the gas phase. In order to achieve a rational and efficient optimization of the process, it is essential to identify the reactive species and to understand the chemical kinetics that govern the production of these precursor species for film growth. In this Account, we report recent progress in unraveling the complex gas-phase reaction chemistry in the HWCVD growth of silicon carbide thin films using organosilicon compounds as single-source precursors. We have demonstrated that laser ionization mass spectrometry is a powerful diagnostic tool for studying the gas-phase reaction chemistry when combined with the methods of isotope labeling and chemical trapping. The four methyl-substituted silane molecules, belonging to open-chain alkylsilanes, dissociatively adsorb on W and Ta filaments to produce methyl radical and H2 molecule. Under the typical deposition pressures, with increasing number of methyl substitution, the dominant chemistry occurring in the gas phase switches from silylene/silene reactions to free-radical short chain reactions. This change in dominant reaction intermediates from silylene/silene to methyl radicals explains the observation from thin film deposition that silicon carbide films become more C-rich with a decreasing number of Si-H bonds in the four precursor molecules. In the case of cyclic monosilacyclobutanes, we have shown that ring-opening reactions play a vital role in characterizing the reaction chemistry. On the other hand, exocyclic Si-H(CH3) bond cleavages are more important in the less-puckered disilacyclobutane molecules. Metal filaments are essential in HWCVD since they serve as catalysts to decompose precursor gases to reactive species, which initiate gas-phase reaction chemistry and thin film growth. We discuss the structural changes in metal filaments when exposed to various precursor gases. Depending on the nature of the radical intermediates formed from the hot-wire decomposition and subsequent gas-phase reactions, metal silicides and carbides can be formed. Overall, study of the gas-phase reaction chemistry in HWCVD provides important knowledge of the chemical species produced prior to their deposition on a substrate surface. This helps in identifying the major contributor to alloy formation on the filament itself and the film growth, and consequently, in determining the properties of the deposited films. An integrated knowledge of the gas-phase reaction chemistry, filament alloy formation, and thin film deposition is required for an efficient deposition of high-quality thin films and nanomaterials.

Theoretical study of the kinetics of chlorine atom abstraction from chloromethanes by atomic chlorine

Ab initio calculations at the G3 level were used in a theoretical description of the kinetics and mechanism of the chlorine abstraction reactions from mono-, di-, tri- and tetra-chloromethane by chlorine atoms. The calculated profiles of the potential energy surface of the reaction systems show that the mechanism of the studied reactions is complex and the Cl-abstraction proceeds via the formation of intermediate complexes. The multi-step reaction mechanism consists of two elementary steps in the case of CCl4 + Cl, and three for the other reactions. Rate constants were calculated using the theoretical method based on the RRKM theory and the simplified version of the statistical adiabatic channel model. The temperature dependencies of the calculated rate constants can be expressed, in temperature range of 200–3,000 K as\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\begin{array}{*{20}c} {k\\left( {\\mathrm{C}{{\\mathrm{H}}_3}\\mathrm{C}\\mathrm{l}+\\mathrm{Cl}} \\right) = 2.08\ imes {10^{-11 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{1.63 }}\ imes\\exp \\left( {{-12780 \\left/ {\\mathrm{T}} \\right.}} \\right)\\ }{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ {k\\left( {\\mathrm{C}{{\\mathrm{H}}_2}\\mathrm{C}{{\\mathrm{l}}_2}+\\mathrm{Cl}} \\right) = 2.36\ imes {10^{-11 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{1.23 }}\ imes\\exp \\left( {{-10960 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ {k\\left( {\\mathrm{C}\\mathrm{HC}{{\\mathrm{l}}_3}+\\mathrm{Cl}} \\right) = 5.28\ imes {10^{-11 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{0.97 }}\ imes\\exp \\left( {{-9200 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ {k\\left( {\\mathrm{C}\\mathrm{C}{{\\mathrm{l}}_4}+\\mathrm{Cl}} \\right) = 1.51\ imes {10^{-10 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{0.58 }}\ imes \\exp \\left( {{-7790 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ \\end{array} $$\\end{document} The rate constants for the reverse reactions CH3/CH2Cl/CHCl2/CCl3 + Cl2 were calculated via the equilibrium constants derived theoretically. The kinetic equations\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\begin{array}{*{20}c} {k\\left( {\\mathrm{C}{{\\mathrm{H}}_3}+\\mathrm{C}{{\\mathrm{l}}_2}} \\right) = 6.70\ imes {10^{-13 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{1.51 }}\ imes \\exp \\left( {{270 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ {k\\left( {\\mathrm{C}{{\\mathrm{H}}_2}\\mathrm{C}\\mathrm{l}+\\mathrm{C}{{\\mathrm{l}}_2}} \\right) = 7.34\ imes {10^{-14 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{1.43 }}\ imes \\exp \\left( {{390 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ {k\\left( {\\mathrm{C}\\mathrm{HC}{{\\mathrm{l}}_2}+\\mathrm{C}{{\\mathrm{l}}_2}} \\right) = 6.81\ imes {10^{-14 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{1.60 }}\ imes \\exp \\left( {{-370 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ {k\\left( {\\mathrm{C}\\mathrm{C}{{\\mathrm{l}}_3}+\\mathrm{C}{{\\mathrm{l}}_2}} \\right) = 1.43\ imes {10^{-13 }}\ imes {{{\\left( {{{\\mathrm{T}} \\left/ {300 } \\right.}} \\right)}}^{1.52 }}\ imes \\exp \\left( {{-550 \\left/ {\\mathrm{T}} \\right.}} \\right)}{\\mathrm{c}{{\\mathrm{m}}^3}\\mathrm{molecul}{{\\mathrm{e}}^{-1 }}{{\\mathrm{s}}^{-1 }}} \\\\ \\end{array} $$\\end{document}allow a very good description of the reaction kinetics. The derived expressions are a substantial supplement to the kinetic data necessary to describe and model the complex gas-phase reactions of importance in combustion and atmospheric chemistry.

Interdependency of Gas Phase Intermediates and Chemical Vapor Deposition Growth of Single Wall Carbon Nanotubes

The main gas phase intermediates, leading the efficient chemical vapor deposition (CVD) growth of single wall carbon nanotubes (SWCNTs), have been explored through systematic experimental and theoretical studies. The growth efficiencies of the basic radical/neutral species (sp2 C2: C2H3/C2H4, sp3 C2: C2H5/C2H6, and sp3 C1: CH3/CH4) have been compared by supplying C2H4, C2H6, and CH4, as carbon sources to grow SWCNTs. The gaseous composition of the exhaust was analyzed by an in situ direct sampling mass spectrometric technique using vacuum ultraviolet (VUV)-single photon ionization (SPI)-time-of-flight mass spectrometry (TOFMS). For verification via theoretical prediction, a CHEMKIN calculation was performed. A kinetic analysis of the experimental and theoretical results was compared with thermal decomposition phenomena of the used hydrocarbons, and hence, it was concluded that the key gas phase intermediates produced from the complex gas phase reactions as a final and efficient species capable of initiating the CVD growth of SWCNTs are sp2 C2 species, C2H3/C2H4. Additional significance is the production of highly pure SWCNTs from C2H6 since to date production of either only multiwall carbon nanotubes (MWCNTs) or a mixture of MWCNTs and SWCNTs have been reported. This result will be beneficial for selecting suitable hydrocarbons for the efficient growth of SWCNTs.

Kinetic and Microstructure of SiC Deposited from SiCl 4-CH 4-H 2

Silicon carbide was prepared from SiCl 4-CH 4-H 2 gaseous precursors by isothermal, isobaric chemical vapor deposition (CVD) at atmospheric pressure and temperatures ranging from 900°C to 1100°C. Kinetic studies showed that carbosilane of SiH 2Cl 2, SiHCl 3 and SiCl 2 formed from decomposition of SiCl 4 and CH 4 contributed to the deposition of hexangular facet and granular pebble structured SiC. An average apparent activation energy of 152 kJ·mol −1 was determined. The overall CVD process was controlled not only by the surface reactions but also by complex gas phase reactions. The as-deposited thin film was characterized using scanning electron microscopy, X-ray diffraction and transmission electron microscopy, these analysis showed that the deposited thin film consisted of pure phase of the β-SiC, the growth morphology of β-SiC differs from hexangular facet to granular pebble structures, which varied with substrate length and CVD temperature.

Effect of carbon monoxide addition to the anode of a molten carbonate fuel cell

Abstract This study attempts to characterize the gas-phase reactions at the anode of a molten carbonate fuel cell by the addition of carbon monoxide and carbon dioxide. Carbon dioxide addition causes a rapid negative voltage shift. A constant voltage is maintained during the addition at open-circuit state. This indicates that the water gas shift (wgs) reaction which accompanies the addition of carbon dioxide is a fast reaction. Addition of carbon monoxide results in slow shifts in negative and positive voltages and suggests that carbon monoxide gives rise to complex gas-phase reactions at the anode. The Boudouard reaction prevails at the anode on addition of carbon monoxide at low partial pressures of carbon dioxide, i.e. H 2 :CO 2 =90:10 to 80:20 mol%, while the wgs reaction is dominant at higher carbon dioxide ratios. In a polarized state, the wgs reaction appears to be dominant, as opposed to the Boudouard reaction, even at a low CO 2 partial pressure of H 2 :CO 2 =90:10 mol%. This is probably due to an increase in the partial pressure of carbon dioxide caused by the anodic reactions.

Metalorganic precursor decomposition and oxidation mechanisms in plasma-enhanced ZrO2 deposition

We investigated the gas phase reaction mechanisms in the ZrO2-deposition plasma using zirconium tert-butoxide (ZTB) as a metalorganic precursor, Ar as a carrier of the ZTB vapor, and O2 as an oxidant using quadrupole mass spectrometry (QMS). Zirconium containing ions including Zr+, ZrO+, ZrO2H+, ZrO3H3+, and ZrO4H5+ were clearly observed in the plasma, and ions of higher zirconium oxidation states become progressively favored at higher O2-to-ZTB carrying Ar flow rate ratio (O2/Ar), increased chamber pressure, and decreased microwave power. The average oxidation state calculated from the partition of ZrOxHy+ varied from 0.5 to 2.1 in the process range covering O2/Ar of 0 to 4, pressure of 5 to 40 mTorr, and power of 150 to 700 W. Based on the QMS analyses, we proposed two main opposing reaction paths responsible for the complex gas phase reactions, i.e., serial dissociations and serial oxidations. The increase in the electron temperature and density resulted in the shift of ZrOxHy+ to lower oxidation states by enhancing the dissociation of Zr–O bond and by depleting oxygen through gas phase reactions. The repartitioning of the ZrOxHy+ species was also contributed by their different Zr–O dissociation energies. To ascertain the effect of various process variables, we monitored the time evolutions of O2+ and ZrOxHy+ intensities as we abruptly change a process variable: the chemical effect (O2/Ar) led to gradual changes in their intensities, whereas physical effects (pressure and power) caused an abrupt step change in accordance with an instant response of the plasma electrons.

Laser ablation and static secondary ion mass spectrometry capabilities in the characterization of inorganic materials

Recently, mass spectrometry techniques such as laser ablation and static secondary ion mass spectrometry (LA-MS and s-SIMS, respectively) have been successfully applied to the characterization of inorganic compounds in solid state phase: s-SIMS is known as a surface analytical technique whereas LA-MS involves atoms in a greater thickness (bulk). In the case of s-SIMS, the direct ejection of ions from the surface upon primary ion sputtering for ion fluence down to 10 13 ions/cm 2, leads to a simple and direct diagnostic by comparing the spectra to databases. On the opposite, characterization of inorganic compounds by means of LA-MS is not immediate due to the most detected ions are issued from complex gas phase reactions. This feature can be successfully applied to investigate matter transfer processes occurring during pulsed-laser deposition (PLD) experiments. By the mean of a systematic and comparative study of LA-MS and s-SIMS spectra for binary (Cu–O) or ternary (Fe–Cr–O) oxide systems, we demonstrate that both techniques are complementary to each other in the field of material science.

Chemical vapor infiltration of carbon – revised: Part I: Model simulations

Carbon deposition from light hydrocarbons and especially from methane is a homogeneous–heterogeneous process in which complex gas phase reactions in series are competing with complex surface reactions. Models of these deposition processes, proposed for carbon deposition from methane, are used to simulate deposition profiles in capillaries, 1 mm in diameter. The influence of the length of the reaction sequence of the gas phase reactions, the methane pressure, the capillary depth and the residence time of the gas (methane) outside of the capillary were investigated. It is shown that the deposition gradients increase from the mouth to the depth of the capillary as long as gas phase reactions outside of the capillary are limited by a short residence time of the gas. Increasing length of the reaction sequence, increasing methane pressure and capillary depth enhance the gradient. Strongly increasing gradients at short residence times correlate with strongly decreasing (inverse) gradients at long residence times. An experimental confirmation of these results is presented in Part II of the paper.

Nonlinear dynamics of surface stabilized premixed and diffusion flames: current trends and future directions

Instabilities of premixed and diffusion hydrogen/air flames near surfaces are modeled using complex gas-phase reaction chemistry and numerical bifurcation theory. Steady-state multiplicities are computed using a combined dynamically adaptive multiple weights arc-length continuation algorithm and Newton's method, and their dynamics is examined through local stability analysis and direct numerical integration. For premixed flames, it is found that Hopf bifurcations exist over a wide range of pressure, and the pressure–temperature stability diagram exhibits many similarities to experimental results and simulations in a continuous-stirred tank reactor. It is shown that reaction exothermicity is not a prerequisite for oscillations but can expand the regime over which oscillations are observed. We report oscillations for diffusion flames at atmospheric pressure, for the first time, as the surface fuel flow rate decreases toward the thermally quenched flammability limit. Overall, the bifurcation behavior of a diffusion flame exhibits a remarkable similarity to that of a premixed flame by an appropriate choice of parameters. Implications for oscillations in condensed fuels prior to flame extinction and future research directions are briefly discussed.

CVD in Hot Wall Reactors—The Interaction Between Homogeneous Gas-Phase and Heterogeneous Surface Reactions

The paper is concerned with chemical vapor deposition in hot wall reactors and in particular with the interaction of homogeneous gas-phase and heterogeneous surface reactions. Based on model considerations it is shown that this interaction has a tremendous influence on the deposition chemistry and kinetics in all cases in which the precursor gas undergoes complex gas-phase reactions. The decisive parameter determining the interaction is given by the ratio of free volume of the deposition space and size of the surface area of the substrate; it is termed the “third parameter” of chemical vapor deposition. Predictions from the model are experimentally confirmed using results on chemical vapor deposition of pyrolytic carbon from methane. The importance of this “third parameter” of chemical vapor deposition in investigations of kinetics and for technical processes of chemical vapor deposition and infiltration is discussed in the conclusion.

ChemInform Abstract: The Modeling of Complex Gas Phase Reactions: From Expert Systems to Supercomputers

ChemInformVolume 21, Issue 44 Reviews ChemInform Abstract: The Modeling of Complex Gas Phase Reactions: From Expert Systems to Supercomputers G. M. COME, G. M. COME Univ. Nancy I, 54000 Nancy, Fr.Search for more papers by this authorG. SCACCHI, G. SCACCHI Univ. Nancy I, 54000 Nancy, Fr.Search for more papers by this author G. M. COME, G. M. COME Univ. Nancy I, 54000 Nancy, Fr.Search for more papers by this authorG. SCACCHI, G. SCACCHI Univ. Nancy I, 54000 Nancy, Fr.Search for more papers by this author First published: October 30, 1990 https://doi.org/10.1002/chin.199044383Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue44October 30, 1990 RelatedInformation

Some aspects of the evaluation of kinetic data

The need for reliable reaction rate data for the analysis of complex gas-phase reaction systems has stimulated the production of tables of critically evaluated rate constants. The procedures and criteria used in such evaluations are outlined and some of their limitations discussed. The part played by theory in guiding the evaluator is discussed and illustrated with examples from decomposition--combination reactions. Attention is drawn to the particular problems associated with evaluation of the temperature dependence of rate constants. 2 figures.