Free-energy reaction surface

Fig. 4 Free energy reaction coordinate profiles that illustrate a change in the relative kinetic barriers for partitioning of carbocations between nucleophilic addition of solvent and deprotonation resulting from a change in the curvature of the potential energy surface for the nucleophile addition reaction. This would correspond to an increase in the intrinsic barrier for the thermoneutral carbocation-nucleophile addition reaction.

If the free energy—reaction coordinate curves are symmetrical and linear at the cross points A and A of the energy surfaces in Fig. 4, geometrical considerations result in BC = CA [10] and... 

Explain, for a reaction A > B, how the potential energy change on a PES is related to the enthalpy change of the reaction. What would be the problem with calculating a free energy/geometry surface ... 

Modern DFT has become a powerful tool to understand, predict, and discover electrochemical catalysts with improved ORR activity and stability. Computational free energy reaction diagrams provide insight into the potential-determining elementary reaction step of the ORR as a function of atomistic descriptors (surface-related properties) of the catalyst material. DFT-based volcano relations have been established pointing to improved catalyst systems. 

The relative stability of surfaces of different composition in contact with reactive gases is determined by the free energy of surface formation which can be calculated from first principles. The formalism in the context of metal oxides is now well established [12-15] and is applied here to the specific reaction conditions of AIF3 [16]. Modelling the AIF3 surface as a periodic slab of material, the surface free energy is given by [17]... 

This difference is a measure of the free-energy driving force for the development reaction. If the development mechanism is treated as an electrode reaction such that the developing silver center functions as an electrode, then the electron-transfer step is first order in the concentration of D and first order in the surface area of the developing silver center (280) (Fig. 13). Phenomenologically, the rate of formation of metallic silver is given in equation 17,... 

This section contains a brief review of the molecular version of Marcus theory, as developed by Warshel [81]. The free energy surface for an electron transfer reaction is shown schematically in Eigure 1, where R represents the reactants and A, P represents the products D and A , and the reaction coordinate X is the degree of polarization of the solvent. The subscript o for R and P denotes the equilibrium values of R and P, while P is the Eranck-Condon state on the P-surface. The activation free energy, AG, can be calculated from Marcus theory by Eq. (4). This relation is based on the assumption that the free energy is a parabolic function of the polarization coordinate. Eor self-exchange transfer reactions, we need only X to calculate AG, because AG° = 0. Moreover, we can write... 

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