scholarly journals Computational Kinetics by Variational Transition-State Theory with Semiclassical Multidimensional Tunneling: Direct Dynamics Rate Constants for the Abstraction of H from CH3OH by Triplet Oxygen Atoms

2017 ◽  
Vol 121 (8) ◽  
pp. 1693-1707 ◽  
Author(s):  
Rubén Meana-Pañeda ◽  
Xuefei Xu ◽  
He Ma ◽  
Donald G. Truhlar
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Direct Dynamics ◽  
Multidimensional Tunneling ◽  
Variational Transition State ◽  
Oxygen Atoms

scholarly journals Barrierless association of CF2and dissociation of C2F4by variational transition-state theory and system-specific quantum Rice–Ramsperger–Kassel theory

2016 ◽  
Vol 113 (48) ◽  
pp. 13606-13611 ◽  
Author(s):  
Junwei Lucas Bao ◽  
Xin Zhang ◽  
Donald G. Truhlar
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Dissociation Rate ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Exchange Correlation ◽  
Direct Dynamics ◽  
Specific Quantum ◽  
Variational Transition State

Bond dissociation is a fundamental chemical reaction, and the first principles modeling of the kinetics of dissociation reactions with a monotonically increasing potential energy along the dissociation coordinate presents a challenge not only for modern electronic structure methods but also for kinetics theory. In this work, we use multifaceted variable-reaction-coordinate variational transition-state theory (VRC-VTST) to compute the high-pressure limit dissociation rate constant of tetrafluoroethylene (C2F4), in which the potential energies are computed by direct dynamics with the M08-HX exchange correlation functional. To treat the pressure dependence of the unimolecular rate constants, we use the recently developed system-specific quantum Rice–Ramsperger–Kassel theory. The calculations are carried out by direct dynamics using an exchange correlation functional validated against calculations that go beyond coupled-cluster theory with single, double, and triple excitations. Our computed dissociation rate constants agree well with the recent experimental measurements.

Dual-Level Direct Dynamics Studies on the Hydrogen Abstraction Reactions of CH2CH3 - n Xn+HBr (X=Cl, Br and n=1, 2)

2012 ◽  
Vol 65 (2) ◽  
pp. 160
Author(s):  
Li Wang ◽  
Jianxiang Zhao ◽  
Hongqing He ◽  
Jinglai Zhang
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Single Point ◽  
State Theory ◽  
Stationary Points ◽  
Variational Transition State Theory ◽  
Point Energy ◽  
Direct Dynamics ◽  
Variational Transition State

The reactions of the HBr molecule with CH2CH2Cl (reaction R1), CH2CHCl2 (R2), CH2CH2Br (R3) and CH2CHBr2 (R4) are investigated by a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points were calculated at the MPW1K/6–311+G(d,p) and BMK/6–311+G(d,p) levels. To refine the reaction enthalpy and energy barrier height of each reaction, single-point energy calculations were carried out by the G2M(RCC5) method based on the geometries optimized at the above-mentioned two levels. Using the canonical variational transition state theory or the canonical variational transition state theory with the small-curvature tunneling correction, the rate constants of HBr with CH2CH2Cl (R1), CH2CHCl2 (R2), CH2CH2Br (R3), and CH2CHBr2 (R4) were calculated over a wide temperature range of 200–2000 K at the G2M(RCC5)//MPW1K/6–311+G(d,p) level. The effect of chlorine or bromine substitution on the ethyl radical reactivity is discussed. Finally, the total rate constants are fitted by two models, i.e. three-parameter and four-parameter expressions.

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