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arXiv 1504.02302cond-mat.soft
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球形孔中几种胶体的结构、热力学性质和phase diagrams

Structure, thermodynamic properties, and phase diagrams of few colloids confined in a spherical pore

Iván Paganini, Claudio Pastorino, Ignacio Urrutia

摘要:

在正则系综下,采用事件驱动的分子动力学模拟,研究了一个封闭在小球腔中的少量胶体体系。胶体粒子通过短程方阱势相互作用,该势考虑了胶体间相互作用的基本要素吸引和排斥体积排斥。在非均匀流体理论的框架下,我们分析了这个少体封闭系统的结构和热力学性质。对关联函数和密度分布的空腔被用来确定系统的结构和空间特性的不均匀性。还分析了壁面压力、内能和表面量(如表面张力和吸附)在整个密度、温度和颗粒数范围内的变化。我们的特点是系统的结构从2到6个禁闭粒子作为密度和温度的函数,确定了独特的定性行为遍布热力学平面$T-ρ$在几个粒子等价的宏观系统的相图。应用扩展的对应态定律,将方阱相互作用映射到Asakura-Oosawa模型。我们明确地链接的温度在封闭的方井流体中的聚合物在Asakura-Oosawa模型的等效包装分数。使用这种方法,我们研究了有限的系统中的几个胶体的胶体-聚合物混合物。

英文摘要:

We study a system of few colloids confined in a small spherical cavity by event driven molecular dynamics simulations in the canonical ensemble. The colloidal particles interact through a short range square-well potential, which takes into account the basic elements of attraction and excluded-volume repulsion of the interaction among colloids. We analyze the structural and thermodynamic properties of this few-body confined system in the framework of the theory of inhomogeneous fluids. Pair correlation functions and density profiles across the cavity are used to determine the structure of the system and the spatial characteristics of its inhomogeneities. Pressure on the walls, internal energy and surface quantities such as surface tension and adsorption are also analyzed for the whole range of densities, temperatures and number of particles considered. We have characterized the structure of systems from 2 to 6 confined particles as function of density and temperature, identifying the distinctive qualitative behaviors all over the thermodynamic plane $T-ρ$ in a few-particle equivalence to phase diagrams of macroscopic systems. Applying the extended law of corresponding states the square well interaction is mapped to the Asakura-Oosawa model for colloid-polymer mixtures. We link explicitly the temperature in the confined square-well fluid to the equivalent packing fraction of polymers in the Asakura-Oosawa model. Using this approach we study the confined system of few colloids in a colloid-polymer mixture.

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