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arXiv 1209.2267cond-mat.softcond-mat.mtrl-sci
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近表面片状胶体粒子性质的Monte Carlo和密度泛函研究

Properties of patchy colloidal particles close to a surface: a Monte Carlo and density functional study

Nicoletta Gnan, Daniel de las Heras, José Maria Tavares, Margarida M. Telo da Gama, Francesco Sciortino

摘要:

利用蒙特卡罗模拟和密度泛函理论研究了硬壁附近的片状粒子模型的行为。两个DFT方法,基于Wertheim的一阶微扰理论的关联自由能的均匀和非均匀版本。我们评估,通过模拟和理论,流体的平衡体相图和分析的表面性质的两个isochores,其中之一是接近液体侧的气液共存曲线。我们发现,密度分布附近的壁交叉从一个典型的高温吸附剖面的低温解吸一个,等容线接近共存。我们将这种行为与散装网络液体的性质联系起来,并发现在这种情况下,理论描述是相当准确的。然而,在非常低的温度下,形成几乎完全键合的网络,并且模拟揭示了DFT未捕获的第二吸附制度。我们跟踪这种失败的粒子,这被发现表现出表面诱导的取向顺序在这个政权的取向相关性的忽视。

英文摘要:

We investigate the behavior of a patchy particle model close to a hard-wall via Monte Carlo simulation and density functional theory (DFT). Two DFT approaches, based on the homogeneous and inhomogeneous versions of Wertheim's first order perturbation theory for the association free energy are used. We evaluate, by simulation and theory, the equilibrium bulk phase diagram of the fluid and analyze the surface properties for two isochores, one of which is close to the liquid side of the gas-liquid coexistence curve. We find that the density profile near the wall crosses over from a typical high-temperature adsorption profile to a low-temperature desorption one, for the isochore close to coexistence. We relate this behavior to the properties of the bulk network liquid and find that the theoretical descriptions are reasonably accurate in this regime. At very low temperatures, however, an almost fully bonded network is formed, and the simulations reveal a second adsorption regime which is not captured by DFT. We trace this failure to the neglect of orientational correlations of the particles, which are found to exhibit surface induced orientational order in this regime.

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