| Summary: | 碩士 === 國立中央大學 === 物理研究所 === 90 ===
Abstract
We apply the equilibrium and the non-equilibrium molecular dynamics sim-ulationsto study the dynamic properties of electrolytes in nanopores. The primitive model and the restrictive primitive model widely used in the sta-tistical mechanics of liquid-state theory were used to model the electrolytes. The electrolytic ions were immersed in water, treated in this work as either a
dielectric continuum ignoring the size of solvent molecules or a macroscopic dielectric continuum (polar property) plus neutral soft spheres, and the whole system is put in a con‾ned space. To simulate a condition closer to processes of practical interest and yet maintain the imulation computationally manage-able,
we consider an in‾nitely long and uncharged cylindrical tube. The equi-librium property of self-di®usion coe± cent and the non-equilibrium property of electric conductivity are computed in terms of electrolytic concentration, particle size and cylindrical radius. Results of simulations for the continuum solvent restrictive primitive model and continuum solvent primitive modelshow normal behavior for the di®usion
coeefcient D vs pore radius R, i.e.,
D decreases with decreasing R, at ionic concentration c¸ =0.1 M, display R-independence
of D at certain threshold c¸ , and an anomalous increase in D
with reducing R at a lower c¸ =0.025 M. The mechanism of the anomaly is
interpreted to arise from the energetic and entropic factors. For the discrete
solvent primitive model, the simulated D is about two order of magnitude less
than the continuum solvent primitive model. This di®erence in D is attributed
to the solvation e®ect. Similar disparities between these latter results were
obtained by others for the discrete restrictive primitive model.
|
|---|
