Potential-energy surfaces Profile

Wang YX, Balbuena PB. 2005b. Potential energy surface profile of the oxygen reduction reaction on a Pt cluster Adsorption and decomposition of OOH and H2O2. J Chem Theory Comput 1 935-943. 

C2H5+ + H2, where at least one high energy pentacoordinate structure is located as an intermediate (minimum on the potential energy surface profile) (27). 

Tresadern G, H Wang, PF Faulder, NA Burton, IH Hillier (2003) Extreme tunnelling in methylamine dehydrogenase revealed by hybrid QM/MM calculations potential energy surface profile for methylamine and ethanolamine substrates and kinetic isotope effect values. Mol. Phys. 101 (17) 2775-2784... 

The calculations of potential energy surface profiles done in Ref. [85] showed as well that the main route of decomposition is consistent with the evolution of formaldehyde and upon a further temperature increase - with that of CO and H2. However, it is not ruled out that at high temperatures of the grafted organic group destruction there are both heterolytic and homolytic processes. 

Wang, Y. Balbuena, P. B. Potential Energy Surface Profile of the Oxygen Reduction Reaction on a Pt Cluster Adsorption and Decomposition of OOH and H2O2. J. Chem. Theory and Comp. 2005, 1, 935-943. 

Fig. 11.5 Potential energy surface profile for the oxygen reduction reaction at the standard hydrogen electrode potential scale the proton was modeled by two shells of water molecules, H 0H2(H20)3(H20),5, and the data in parentheses are Gibbs free energies [50]...

One group has successfiilly obtained infonnation about potential energy surfaces without measuring REPs. Instead, easily measured second derivative absorption profiles are obtained and linked to the fiill RRS spectrum taken at a single incident frequency. In this way, the painstaking task of measuring a REP is replaced by carefiilly recording the second derivative of the electronic absorption spectrum of the resonant transition [, 59],... 

Note that since the profile of the lower adiabatic potential energy surface for the proton depends on the coordinates of the medium molecules, the zeroth-order states and the diabatic potential energy surfaces depend also on the coordinates of the medium molecules. The double adiabatic approximation is essentially used here the electrons adiabatically follow the motion of all nuclei, while the proton zeroth-order states adiabatically follow the change of the positions of the medium molecules. 

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.

All the calculated equilibrium structures and transition states on the potential energy surfaces of the reaction A are shown in Figures 2 to 4. The reaction potential energy profile is shown in Figure 5. 

This reaction profile also illustrates one of the other important challenges in the study of transition metal systems, namely that the metal-containing active site often has several accessible spin states. Specifically in the case of Fe(IV)=0, the triplet, quintet, and septet spin states. Consequently, the reaction can, in principle, proceed on different electronic potential energy surfaces and it is necessary to test all possibilities when exploring a reaction surface. This has been labeled two-state reactivity and has been elaborated by Shaik, Schwarz, Schroder, and co-workers (36—40). In the case of TauD, the results show that the reaction is only feasible on the quintet surface, in agreement with earlier DFT studies (11,41 —45). 

---