Monte Carlo trajectory and master equation simulation of the nonequilibrium dissociation rate coefficient for Ar+H2→Ar+2H at 4500 K

1987 ◽  
Vol 86 (5) ◽  
pp. 2697-2716 ◽  
Author(s):  
Kenneth Haug ◽  
Donald G. Truhlar ◽  
Normand C. Blais
Keyword(s):  
Monte Carlo ◽  
Master Equation ◽  
Rate Coefficient ◽  
Dissociation Rate ◽  
Nonequilibrium Dissociation ◽  
Master Equation Simulation

scholarly journals Direct Kinetic Measurements and Master Equation Modelling of the Unimolecular Decomposition of Resonantly-Stabilized CH2CHCHC(O)OCH3 Radical and an Upper Limit Determination for CH2CHCHC(O)OCH3 + O2 Reaction

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1251-1268 ◽  
Author(s):  
Satya Prakash Joshi ◽  
Prasenjit Seal ◽  
Timo Theodor Pekkanen ◽  
Raimo Sakari Timonen ◽  
Arrke J. Eskola
Keyword(s):  
Master Equation ◽  
Density Functional ◽  
Rate Coefficient ◽  
Decomposition Kinetics ◽  
Basis Sets ◽  
Stationary Points ◽  
Unimolecular Decomposition ◽  
Kinetic Measurements ◽  
Point Energy ◽  
Upper Limit

AbstractMethyl-Crotonate (MC, (E)-methylbut-2-enoate, CH3CHCHC(O)OCH3) is a potential component of surrogate fuels that aim to emulate the combustion of fatty acid methyl ester (FAME) biodiesels with significant unsaturated FAME content. MC has three allylic hydrogens that can be readily abstracted under autoignition and combustion conditions to form a resonantly-stabilized CH2CHCHC(O)OCH3 radical. In this study we have utilized photoionization mass spectrometry to investigate the O2 addition kinetics and thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical. First we determined an upper limit for the bimolecular rate coefficient of CH2CHCHC(O)OCH3 + O2 reaction at 600 K (k ≤ 7.5 × 10−17 cm3 molecule−1 s−1). Such a small rate coefficient suggest this reaction is unlikely to be important under combustion conditions and subsequent efforts were directed towards measuring thermal unimolecular decomposition kinetics of CH2CHCHC(O)OCH3 radical. These measurements were performed between 750 and 869 K temperatures at low pressures (<9 Torr) using both helium and nitrogen bath gases. The potential energy surface of the unimolecular decomposition reaction was probed at density functional (MN15/cc-pVTZ) level of theory and the electronic energies of the stationary points obtained were then refined using the DLPNO-CCSD(T) method with the cc-pVTZ and cc-pVQZ basis sets. Master equation simulations were subsequently carried out using MESMER code along the kinetically important reaction pathway. The master equation model was first optimized by fitting the zero-point energy corrected reaction barriers and the collisional energy transfer parameters $\Delta{E_{{\text{down}},\;{\text{ref}}}}$ and n to the measured rate coefficients data and then utilize the constrained model to extrapolate the decomposition kinetics to higher pressures and temperatures. Both the experimental results and the MESMER simulations show that the current experiments for the thermal unimolecular decomposition of CH2CHCHC(O)OCH3 radical are in the fall-off region. The experiments did not provide definite evidence about the primary decomposition products.

scholarly journals Time-Resolved Measurements and Master Equation Modelling of the Unimolecular Decomposition of CH3OCH2

2020 ◽  
Vol 234 (7-9) ◽  
pp. 1233-1250 ◽  
Author(s):  
Arrke J. Eskola ◽  
Mark A. Blitz ◽  
Michael J. Pilling ◽  
Paul W. Seakins ◽  
Robin J. Shannon
Keyword(s):  
Energy Transfer ◽  
Master Equation ◽  
Rate Coefficient ◽  
Zero Point ◽  
Buffer Gas ◽  
Unimolecular Decomposition ◽  
Time Resolved ◽  
Point Energy ◽  
Wide Range ◽  
Transfer Parameters

AbstractThe rate coefficient for the unimolecular decomposition of CH3OCH2, k1, has been measured in time-resolved experiments by monitoring the HCHO product. CH3OCH2 was rapidly and cleanly generated by 248 nm excimer photolysis of oxalyl chloride, (ClCO)2, in an excess of CH3OCH3, and an excimer pumped dye laser tuned to 353.16 nm was used to probe HCHO via laser induced fluorescence. k1(T,p) was measured over the ranges: 573–673 K and 0.1–4.3 × 1018 molecule cm−3 with a helium bath gas. In addition, some experiments were carried out with nitrogen as the bath gas. Ab initio calculations on CH3OCH2 decomposition were carried out and a transition-state for decomposition to CH3 and H2CO was identified. This information was used in a master equation rate calculation, using the MESMER code, where the zero-point-energy corrected barrier to reaction, ΔE0,1, and the energy transfer parameters, ⟨ΔEdown⟩ × Tn, were the adjusted parameters to best fit the experimental data, with helium as the buffer gas. The data were combined with earlier measurements by Loucks and Laidler (Can J. Chem.1967, 45, 2767), with dimethyl ether as the third body, reinterpreted using current literature for the rate coefficient for recombination of CH3OCH2. This analysis returned ΔE0,1 = (112.3 ± 0.6) kJ mol−1, and leads to $k_{1}^{\infty}(T)=2.9\times{10^{12}}$ (T/300)2.5 exp(−106.8 kJ mol−1/RT). Using this model, limited experiments with nitrogen as the bath gas allowed N2 energy transfer parameters to be identified and then further MESMER simulations were carried out, where N2 was the buffer gas, to generate k1(T,p) over a wide range of conditions: 300–1000 K and N2 = 1012–1025 molecule cm−3. The resulting k1(T,p) has been parameterized using a Troe-expression, so that they can be readily be incorporated into combustion models. In addition, k1(T,p) has been parametrized using PLOG for the buffer gases, He, CH3OCH3 and N2.

P‐169: Towards Fully Integrated 3D Master Equation — Kinetic Monte Carlo Predictive Device Simulations

2020 ◽  
Vol 51 (1) ◽  
pp. 2022-2023
Author(s):  
Siebe van Mensfoort ◽  
Marc Barbry ◽  
Stefano Gottardi ◽  
Harm van Eersel
Keyword(s):  
Monte Carlo ◽  
Master Equation ◽  
Kinetic Monte Carlo ◽  
Fully Integrated

scholarly journals A master equation simulation for the•OH + CH3OH reaction

2019 ◽  
Vol 150 (8) ◽  
pp. 084105 ◽  
Author(s):  
Thanh Lam Nguyen ◽  
Branko Ruscic ◽  
John F. Stanton
Keyword(s):  
Master Equation ◽  
Master Equation Simulation

The Master Equation for the Dissociation of a Dilute Diatomic Gas. VIII. The Rotational Contribution to Dissociation and Recombination

1973 ◽  
Vol 51 (2) ◽  
pp. 237-259 ◽  
Author(s):  
Tom Ashton ◽  
D. L. S. McElwain ◽  
H. O. Pritchard
Keyword(s):  
Master Equation ◽  
Rate Constant ◽  
Rate Constants ◽  
Transition Probabilities ◽  
Rotational Transition ◽  
Dissociation Rate ◽  
Third Body ◽  
Rotational States ◽  
Dissociation Rate Constants ◽  
Very High

The dissociation of the J = 21 state of H2, and the recombination of atoms into that state, have been examined in detail. The J = 21 state of H2 has two quasi-bound levels, one long-lived and the other short-lived, but the rate constants for dissociation or recombination involving this state are almost completely independent of the tunnelling rates into and out of the quasi-bound levels, and are in fact determined by bottleneck effects occurring lower down the vibrational ladder. Direct integration of the relaxation equations shows that, either excluding or including tunnelling, the dissociation and recombination rate constants obey the rate-quotient law, and that in the latter case the lowest eigenvalue of the relaxation matrix properly reflects the pressure dependence of the dissociation rate constant. Less extensive examination of the dissociation properties of other rotational states indicates that these conclusions are general, except that there is no strong bottleneck effect for very high rotational states (J ≥ 30).It is shown that if full rotational equilibration is assumed, the sum, weighted over all J, of the individual dissociation rate constants leads to an overall dissociation rate constant which is much too high, suggesting strongly that rotational equilibration cannot occur amongst the very high J states.A factored form of the master equation is then examined in which either only T–V or only T–R processes take place, over the temperature range 1500–5000 °K. It is found that in this approximation the upper rotational states are very strongly depleted, and that the Arrhenius temperature coefficients of the dissociation rate constants are between 92 and 94 kcal mol−1, depending upon the choice of rotational transition probabilities. The calculation suggests that one contributory cause of "low activation energies" in dissociation reactions is strong rotational depopulation of the very high rotational states, and its importance in relation to other possible causes is discussed.The smallest eigenvalues of the 177th order matrix representing the dissociation of para-H2 and of the 172nd order matrix representing the dissociation of ortho-H2 confirm that the factored model gives an acceptable representation of the dissociation rate of H2 in this temperature range; hence the conclusions of the factored model in respect of strong rotational depopulation are probably valid. Finally, it is shown that the second smallest eigenvalue of the full relaxation matrix changes by a factor of three at 1500 °K or by a factor of ten at 5000 °K when only rotational transition probabilities are varied, thus identifying the relaxation which immediately precedes the dissociation reaction in a shock wave as a T–VR rather than a T–V relaxation.An exploratory series of calculations for deuterium was carried out for the range of temperatures 700–5000 °K, using the latter model which includes full coupling between rotation, vibration, and dissociation, i.e., using matrices of order 348 and 355 for ortho- and para-deuterium, respectively. These calculations predict that there should be a reversal in the isotope effect for both dissociation and recombination of hydrogen and deuterium as follows: (i) with helium as third body, deuterium should dissociate faster than hydrogen at high temperatures, but below about 2000 °K, the dissociation of deuterium will become the slower of the two processes; (ii) with argon as third body, deuterium should recombine faster than hydrogen at high temperatures, but below about 1000 °K, the recombination of deuterium will become the slower of the two processes; (iii) the rate constants for the recombination of hydrogen by hydrogen and for the recombination of deuterium by deuterium will probably cross over near 1000 °K, indicating a need for experiments in this region of temperature.

Multidimensional master equation and its Monte-Carlo simulation

2013 ◽  
Vol 138 (8) ◽  
pp. 084104
Author(s):  
Juan Pang ◽  
Zhan-Wu Bai ◽  
Jing-Dong Bao
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Master Equation
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