Ab initio Variational Transition State Theory and Master Equation Study of the Reaction (OH)₃SiOCH₂ + CH₃ ⇌ (OH)₃SiOC₂H₅

Abstract

Abstract:In this paper we use variable reaction coordinate variational transition state theory (VRC-TST) to calculate the reaction rate constants for the two reactions, R1: (OH) 3 SiOCH 2 + CH 3 (OH) 3 SiOC 2 H 5 , and R2: CH 2 OH + CH 3 C 2 H 5 OH. The first reaction is an important channel during the thermal decomposition of tetraethoxysilane (TEOS), and its rate coefficient is the main focus of this work. The second reaction is analogous to the first and is used as a basis for comparison. The interaction energies are obtained on-the-fly at the CASPT2(2e,2o)/cc-pVDZ level of theory. A one-dimensional correction to the sampled energies was introduced to account for the energetic effects of geometry relaxation along the reaction path. The computed, high-pressure rate coefficients were A comparison of the computed rates with experimental data shows good agreement and an improvement over previous results. The pressure dependency of the reaction R1 is explored by solving a master equation using helium as a bath gas. The results obtained show that the reaction is only weakly pressure dependent

A big data framework to validate thermodynamic data for chemical species

“…For example, the Reaction Mechanism Generator [1,2] automates the generation of chemical mechanisms for gas-phase systems containing carbon, hydrogen, oxygen, sulfur, and nitrogen. Other approaches have been used to develop models for the gasphase chemistry of common precursors for the formation of various nanoparticles [3,4,5,6].…”

Skeletal chemical mechanism of high-temperature TEOS oxidation in hydrogen–oxygen environment

“…The rate of the ethylene loss from TEOS, TREOS, DEOS and DMDEOS was computed using transition state theory, where a CBS-Q method was employed for accurate estimation of the reaction energetics. The rates of the ethylene loss from EOS and C−C bond cleavage reactions were taken from the literature [24].…”

“…Refinement of the first class of reactions was achieved by using more accurate rate constants for the C 2 H 4 -loss from TEOS, TREOS, DEOS and EOS (see Table 1) as a basis for the remaining analogous reactions. The first three channels were computed in this work, whereas the last one was taken from the calculation of Nurkowski et al [24]. Refinement of the second class of reactions was achieved in the same way by using rate constant coefficient of the C−C bond cleavage in EOS from Nurkowski et al [24].…”

“…The first three channels were computed in this work, whereas the last one was taken from the calculation of Nurkowski et al [24]. Refinement of the second class of reactions was achieved in the same way by using rate constant coefficient of the C−C bond cleavage in EOS from Nurkowski et al [24]. The propagation of the improved rates throughout the analogous species in the mechanism was made under the assumption that species with the same number of hydrocarbon branches react at the same rate and that the rates linearly scale with the number of branches.…”

“…However, before such a complex process can be simulated a proper understanding of the homogenous case is required first. To achieve this, a full model is first created that builds on the mechanism proposed by Nurkowski et al [17] and incorporates rates improvements reported in the previous [24] and present work. The resulting mechanism is then used as the starting point for deriving a reduced mechanism.…”