کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5408043 1506531 2017 54 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Study of cage effect and subdiffusion in Pickering emulsions from Molecular Dynamics simulations
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
Study of cage effect and subdiffusion in Pickering emulsions from Molecular Dynamics simulations
چکیده انگلیسی
In this work, we study the diffusion laws of oil-droplets dispersed in water onto which are strongly adsorbed charged point-like particles (Pickering emulsions). This diffusion that originates from multiple collisions with the molecules of water, is anomalous, due to the presence of relatively strong correlations between the moving oil-droplets. Using Molecular Dynamics simulation, with a pair-potential of Sogami-Ise type, we first observe that the random walkers execute a normal diffusion, at intermediate time, followed by a slow diffusion (subdiffusion) we attribute to the presence of cages, formed by the nearest neighbors (traps). In the cage-regime, we find that the mean-square-displacement increases according to a time-power law, with an anomalous diffusion exponent, α (between 0 and 1). This exponent and the generalized diffusion coefficient are computed varying the relevant parameters (surface charge, density, salt-concentration). We remark that the subdiffusion is significant only for strong surface charges and densities, and low-salt concentrations. The existence of a cage effect is shown computing the velocity auto-correlation function of the random walker. It is found that, in a cage, this function is governed by an underdamped (oscillatory) behavior, for strong densities and surface charges, and low-salt concentration. In the inverse situation, however, we observe that this correlation-function is rather overdamped (non-oscillatory). In the two cases, at large-time, this function fails according to a time-power law, with the exponent α − 2. To validate our simulation data, we propose a memory diffusion theory that is based essentially on a generalized Langevin equation. Finally, we demonstrate that the results from simulations are in good agreement with the predictions of the elaborated theory.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Liquids - Volume 240, August 2017, Pages 1-13
نویسندگان
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