Molecular stmeture simulation

In this chapter, the results of the molecular-dynamies simulation of Ni, Cu and Au in liquid and supercooled liquid states are displayed. The potentials of interatomie interaction within the framework of the embedded-atom method are used to generate realistic atomic configurations. The struetural analysis of the eluster stmeture has been conducted with the use of the bond orientational order parameter of the interatomic bonds. It is shown that the loeal ieosahedral order is present and it enhances at supercooling of the melts of the metals imder discussion. 

Frank [2] was the first who assumed that the stmeture of liquid metals could be described on the basis of ieosahedral packing. Much later [3] the assumption was confirmed by the molecular-dynamics simulation of a supercooled model melt within the framework of Lennard-Jones potentials. 

In this work, we have approaehed the understanding of proton transport with two tasks. In the first task, deseribed above, we have sought to identify the moleeular-level stmeture of PFSA membranes and their relevant interfaees as a funetion of water content and polymer architecture. In the second task, described in this Section, we explain our efforts to model and quantify proton transport in these membranes and interfaces and their dependence on water content and polymer architecture. As in the task I, the tool employed is molecular dynamics (MD) simulation. A non-reactive algorithm is sufficient to generate the morphology of the membrane and its interfaces. It is also capable of providing some information about transport in the system such as diffusivities of water and the vehicular component of the proton diffusivity. Moreover, analysis of the hydration of hydronium ion provides indirect information about the structural component of proton diffusion, but a direct measure of the total proton diffusivity is beyond the capabilities of a non-reactive MD simulation. Therefore, in the task II, we develop and implement a reactive molecular dynamics algorithm that will lead to direct measurement of the total proton diffusivity. As the work is an active field, we report the work to date. 

---