DFT Investigation of the Mechanism and Chemical Kinetics for the Gelation of Colloidal Silica

2013 ◽  
Vol 1547 ◽  
pp. 173-182
Author(s):  
Steven S. Burnett ◽  
James W. Mitchell
Keyword(s):  
Transition State ◽  
Ammonium Chloride ◽  
Rate Constants ◽  
Density Functional ◽  
Reaction Rate ◽  
Colloidal Silica ◽  
Energy Surface ◽  
State Theory ◽  
Functional Theory ◽  
Reaction Rate Constants

ABSTRACTThe mechanism for the gelation reaction of colloidal silica, Si(OH)4 +Si(OH)3 (O)- ----> Si2O8H5- + H2O, by an anionic pathway was investigated using density functional theory(DFT). Using transition state theory, the rate constants were obtained by analyzing the potential energy surface at the reactants, saddle point, and the products. In addition, reaction rate constants were investigated in the presence of ammonium chloride (NH4Cl) and sodium chloride (NaCl). These salts act as catalysts to induce gelation by destabilizing the double layer of colloidal silica to allow for Van der Waal interactions. Furthermore, it was observed that ammonium chloride plays an important role by initiating a hydride transfer allowing the reaction to proceed from the second transition state to the final product.

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

2015 ◽  
Vol 229 (5) ◽  
Author(s):  
Daniel Nurkowski ◽  
Stephen J. Klippenstein ◽  
Yuri Georgievskii ◽  
Marco Verdicchio ◽  
Ahren W. Jasper ◽  
...  
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Master Equation ◽  
Rate Constants ◽  
Transition State Theory ◽  
Reaction Rate ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Reaction Rate Constants ◽  
Variational Transition State

AbstractIn 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)

scholarly journals Application of Transition State Theory to Estimate Diffusion Controlled Bimolecular Reaction Rate Constants.

1981 ◽  
Vol 35b ◽  
pp. 529-531 ◽  
Author(s):  
Vernon D. Parker ◽  
Ann-Marie Eklund ◽  
Toshiaki Nishida ◽  
Curt R. Enzell ◽  
Curt R. Enzell
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Reaction Rate ◽  
Bimolecular Reaction ◽  
State Theory ◽  
Reaction Rate Constants ◽  
Diffusion Controlled

scholarly journals “Transitivity”: A Code for Computing Kinetic and Related Parameters in Chemical Transformations and Transport Phenomena

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3478 ◽  
Author(s):  
Hugo G. Machado ◽  
Flávio O. Sanches-Neto ◽  
Nayara D. Coutinho ◽  
Kleber C. Mundim ◽  
Federico Palazzetti ◽  
...  
Keyword(s):  
Rate Constants ◽  
Reaction Rate ◽  
Reaction Rate Constant ◽  
State Theory ◽  
Chemical Transformations ◽  
Graphical Interface ◽  
Arrhenius Behavior ◽  
Reaction Rate Constants ◽  
Kinetic And Thermodynamic Parameters ◽  
Data Documentation

The Transitivity function, defined in terms of the reciprocal of the apparent activation energy, measures the propensity for a reaction to proceed and can provide a tool for implementing phenomenological kinetic models. Applications to systems which deviate from the Arrhenius law at low temperature encouraged the development of a user-friendly graphical interface for estimating the kinetic and thermodynamic parameters of physical and chemical processes. Here, we document the Transitivity code, written in Python, a free open-source code compatible with Windows, Linux and macOS platforms. Procedures are made available to evaluate the phenomenology of the temperature dependence of rate constants for processes from the Arrhenius and Transitivity plots. Reaction rate constants can be calculated by the traditional Transition-State Theory using a set of one-dimensional tunneling corrections (Bell (1935), Bell (1958), Skodje and Truhlar and, in particular, the deformed ( d -TST) approach). To account for the solvent effect on reaction rate constant, implementation is given of the Kramers and of Collins–Kimball formulations. An input file generator is provided to run various molecular dynamics approaches in CPMD code. Examples are worked out and made available for testing. The novelty of this code is its general scope and particular exploit of d -formulations to cope with non-Arrhenius behavior at low temperatures, a topic which is the focus of recent intense investigations. We expect that this code serves as a quick and practical tool for data documentation from electronic structure calculations: It presents a very intuitive graphical interface which we believe to provide an excellent working tool for researchers and as courseware to teach statistical thermodynamics, thermochemistry, kinetics, and related areas.

Theoretical study on the chemical formation mechanism of a β-myrcene ozonolysis reaction under atmospheric conditions

2012 ◽  
Vol 90 (8) ◽  
pp. 708-715 ◽  
Author(s):  
Yuyang Zhao ◽  
Jing Bai ◽  
Chenxi Zhang ◽  
Chen Gong ◽  
Xiaomin Sun
Keyword(s):  
Rate Constants ◽  
Potential Energy Surfaces ◽  
Density Functional ◽  
Single Point ◽  
State Theory ◽  
Tunneling Effect ◽  
Atmospheric Conditions ◽  
Functional Theory ◽  
Real Atmosphere ◽  
Energy Surfaces

Density functional theory (DFT) was used to study the β-myrcene ozonolysis reaction. The reactants, intermediates, transition states, and products were optimized at the MPWB1K/6–31G(d,p) level. The single-point energies were performed at the MPWB1K/6–311+G(3df,2p) level. The profiles of the potential energy surfaces were constructed and the rate constants of the reaction steps were analyzed. The possible reaction mechanisms for the ozonolysis intermediates in real atmosphere are also discussed. Based on quantum chemistry information, the rate constants were calculated using Rice–Ramsperger–Kassel–Marcus (RRKM) theory and the canonical variational transition-state theory (CVT) with small curvature tunneling effect (SCT). Arrhenius equations of rate constants over the temperature range of 200–800 K are provided, and the lifetimes of the reaction species in the troposphere were estimated according to rate constants.

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