Semiempirical Rate Constants for Complex Chemical Kinetics: First-Principles Assessment and Rational Refinement

2010 ◽  
Vol 50 (5) ◽  
pp. 1194-1197 ◽  
Author(s):  
Matteo Maestri ◽  
Karsten Reuter
Keyword(s):  
Chemical Kinetics ◽  
Rate Constants ◽  
First Principles ◽  
Complex Chemical ◽  
Rational Refinement

Chemical equilibrium and chemical kinetics

2018 ◽  
Author(s):  
Dennis Sherwood ◽  
Paul Dalby
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Gibbs Free Energy ◽  
Chemical Kinetics ◽  
Chemical Equilibrium ◽  
First Principles ◽  
Effect Of Temperature ◽  
Total System ◽  
Free Energies

Building on the previous chapter, this chapter examines gas phase chemical equilibrium, and the equilibrium constant. This chapter takes a rigorous, yet very clear, ‘first principles’ approach, expressing the total Gibbs free energy of a reaction mixture at any time as the sum of the instantaneous Gibbs free energies of each component, as expressed in terms of the extent-of-reaction. The equilibrium reaction mixture is then defined as the point at which the total system Gibbs free energy is a minimum, from which concepts such as the equilibrium constant emerge. The chapter also explores the temperature dependence of equilibrium, this being one example of Le Chatelier’s principle. Finally, the chapter links thermodynamics to chemical kinetics by showing how the equilibrium constant is the ratio of the forward and backward rate constants. We also introduce the Arrhenius equation, closing with a discussion of the overall effect of temperature on chemical equilibrium.

The Importance of Variables and Parameters in Radiolytic Chemical Kinetics Modeling

1988 ◽  
Vol 127 ◽  
Author(s):  
M. G. Piepho ◽  
P. J. Turner ◽  
P. W. Reimus
Keyword(s):  
Chemical Kinetics ◽  
Rate Constants ◽  
Transient Species ◽  
Geologic Repository ◽  
Species Concentration ◽  
Waste Package ◽  
Long Term Performance ◽  
Term Performance ◽  
Over Time

ABSTRACTRadiolysis may significantly affect the long-term performance of nuclear waste packages in a geologic repository. Radiolysis of available moisture and air in an unsaturated or saturated environment will create transient species that can significantly change the pH and/or Eh of the available moisture. These changes can influence rates of containment corrosion, waste form dissolution, and radionuclide solubilities and transport.Many of the pertinent radiochemical reactions are not completely understood, and most of the associated rate constants are poorly characterized. To help identify the important radiochemical reactions, rate constants, species, and environmental conditions, an importance theory code, SWATS (Sensitivity With Adjoint Theory-Sparse version)-LOOPCHEM, has been developed for the radiolytic chemical kinetics model in the radiolysis code LOOPCHEM. The LOOPCHEM code calculates the concentrations of various species in a radiolytic field over time. The SWATS-LOOPCHEM code efficiently calculates: 1) the importance (relative to a defined response of interest) of each species concentration over time, 2) the sensitivity of each parameter of interest, and 3) the importance of each equation in the radiolysis model. The calculated results will be used to guide future experimental and modeling work for determining the importance of radiolysis on waste package performance. A demonstration (the importance of selected concentrations and the sensitivities of selected parameters) of the SWATS-LOOPCHEM code is provided for illustrative purposes, and no attempt is made at this time to interpret the results for waste package performance assessment purposes.

scholarly journals First-principles calculations of anharmonic and deuteration effects on the photophysical properties of polyacenes and porphyrinoids

2020 ◽  
Vol 22 (39) ◽  
pp. 22314-22323 ◽  
Author(s):  
R. R. Valiev ◽  
R. T. Nasibullin ◽  
V. N. Cherepanov ◽  
G. V. Baryshnikov ◽  
D. Sundholm ◽  
...  
Keyword(s):  
Rate Constants ◽  
First Principles ◽  
Conversion Rate ◽  
Internal Conversion ◽  
Photophysical Properties ◽  
New Method ◽  
Lagrangian Multiplier ◽  
First Principles Calculations ◽  
Anharmonic Effects

A new method for calculating internal conversion rate constants (kIC), including anharmonic effects and using the Lagrangian multiplier technique, is proposed.

Rate constants and first-principles trajectories for attack at tetrahedral carbon: Role of molecular orientation on chiral selectivity

2019 ◽  
Author(s):  
Marcos Vinícius C. S. Rezende ◽  
Priscila Gomes dos Santos ◽  
Nayara D. Coutinho ◽  
Federico Palazzetti ◽  
Andrea Lombardi ◽  
...  
Keyword(s):  
Rate Constants ◽  
First Principles ◽  
Molecular Orientation ◽  
Chiral Selectivity
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