Dependence of activation energy

FIGURE 16.1 The dependence of activation energy E on reaction enthalpy A He for reaction of hydrogen atom abstraction by aminyl radical from the C—H bond of alkylperoxyl radical and O—H bond of hydroperoxyl radical calculated by IPM method (see Chapter 6). The points fix the reactions with minimum and maximum enthalpy among known aromatic aminyl radicals. 

Figure 4.1 Dependence of activation energy for viscous flow on melting point for normal metals and semi-metals. Reprinted, by permission, from T. lida and R. I. L. Guthrie, The Physical Properties of Liquid Metals, p. 187. Copyright 1988 by Oxford University Press.

Potentiometric techniques have been used to study autonomous reaction rate oscillations over catalysts and carbon monoxide oxidation on platinum has received a considerable amount of attention43,48,58 Possible explanations for reaction rate oscillations over platinum for carbon monoxide oxidation include, (i) strong dependence of activation energy or heat of adsorption on coverage, (ii) surface temperature oscillations, (iii) shift between multiple steady states due to adsorption or desorption of inert species, (iv) periodic oxidation or reduction of the surface. The work of Sales, Turner and Maple has indicated that the most... 

Figure 6. Dependence of activation energy, E, on heat of reaction, AH, for...

The influence of the additives upon the reaction velocity, K, is reflected through the changes produced in the frequency factor, Ko, and in the activation energy, E. The dependence of activation energy... 

Korablev G.A., Kodolov V I. Dependence of activation energy of chemical reactions upon spatial-energy characteristics of atoms - Chemical physics and mesoscopy. UdRC RAS. Izhevsk. 2001. N<>2.v.3. p.243-254. 

Dependence of activation energy difference on the ratio of pre-exponential factors of transfer (tr) and propagation (p) for the addition of MMA to a radical with the... 

Figure 6 Dependence of activation energy and cluster-cluster distances in 3D arrangements of AU55 clusters. Systems I and II are noncovalently linked, system III are covalently interacting...

Figure 10. Concentration dependence of activation energy (A) at two fields in TPD-PC. p is the intersite distance. (Reproduced from reference 12. Copyright 1984 American Chemical Society.)...

The experimental values obtained for oxides of the first group are somewhat higher between 0.6 and 0.8. Such values are likely to be connected with the dependence of activation energy on the concentration of surface oxygen defects (6). 

The distance Xq in A-units of each point along the semicircle from the unique point in the middle is correlated with the measured activation energy in Figure 5.14. The dependence of activation energy on the distance Xq can be expressed as... 

Here a is a coefficient which is constant for each pair of fixed bonds, the one being cleaved, and the other being formed br is a parameter also constant for a given series of reactions and not very different for different classes of reactions. The latter formula gives non-linear dependence of activation energy on the reaction s enthalpy whereas, less precise Polanyi-Semenov mle predicts a linear dependence ... 

Fig. 26 The log(cooling rate) versus 1/T for PS thin films supported on Si substrate. Inset indicates the thickness dependence of activation energy [63]. Solid symbols represent PS thin films with different film thicknesses...

Freeman [40] demonstrates that solution-diffusion transport theory predicts the existence of an upper bound if diffusion is an activated process, the activation energy depends linearly on the square of the molecular diameter, and solubility depends exponentially on the Lennard-Jones temperature. Although one adjustable parameter is introduced to specify the dependence of activation energy on molecular size, a single value gives excellent predictions of the location of the upper bound for all gas pairs examined. 

The Flynn and Wall method is well-suited to demonstrate the dependence of activation energy and frequency (pre-exponential) factor upon the conversion level. 

Flynn and Wall method. The evaluation according to Flynn and Wall applies measured conversion levels whereas the Ozawa correction of the ASTM E 698-79 incorporated in the DuPont software is based on an empirical function of the dependence of activation energy upon conversion level. 

Implementation of the TSA becomes ambiguous in cases of near degeneracy (e.g., Newton et al., 1991 Broo and Larsson, 1992 Cacelli and Ferretti, 1998 Elliott et al., 1998 Zerner et al., 1980 Newton, 2003 Shin et al, 1996 ) (common in open shell TMCs, where, for example, perturbation of idealized octahedral symmetry may lead to splitting of t2g and Cg states) or other situations where the appropriate choice of tpi and is not obvious.The ehoiee in general involves a tradeoff including thermal access (in the case of initial states), and the state-dependence of activation energy (G ) and coupling (/fif). ... 

---