Proton transport Eigen cation

A second important application of CMD has been to study the dynamics of the hydrated proton. This study involved extensive CMD simulations to determine the proton transport rate in on our Multi-State Empirical Valence Bond (MS-EVB) model for the hydrated proton. = Shown in Fig. 4 are results for the population correlation function, (n(t)n(O)), for the Eigen cation, HsO, in liquid water. Also shown is the correlation function for D3O+ in heavy water. It should be noted that the population correlation function is expected to decay exponentially at long times, the rate of which reflects the excess proton transport rate. The straight line fits (dotted lines) to the semi-log plots of the correlation functions give this rate. For the normal water case, the CMD simulation using the MS-EVB model yields excellent agreement with the experimental proton hopping... 

One of the best investigated, yet not fully understood, transport processes is that in water. So far, the dispute about the Zundel and Eigen ion being the transporting species has been settled partly. Many studies favour the Eigen ion the Zundel ion is considered to be a transition state during the proton transfer. Similar species have been observed in phosphonic and phosphoric acid. However, the presented studies did not put emphasis in the distinction between those two cationic species. 

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