聚集对吸附现象的影响
Effect of aggregation on adsorption phenomena
摘要：
用分子动力学（MD）模拟方法研究了颗粒自组装成小团簇体系在吸引面上的吸附行为。我们假设Lennard-Jones加排斥Yukawa尾相互作用，并专注于小密度。在临界团簇浓度附近的吸引表面（CCCS）的温度的相对增加表现出幂律依赖于壁粒子的吸引力的强度。在低于CCCS的温度下，吸附层由未变形的簇组成，如果壁粒子的吸引力不是太强。以上的CCCS，或为强吸引力导致扁平的吸附聚集体，我们得到一个单层，为强或非常强的吸引力分别由扁平的集群或条纹。来自吸附在壁处的颗粒的累积排斥导致了减缓吸附过程的排斥屏障，并且加入时间随着壁-颗粒吸引力的强度而迅速增长。超出吸附层的颗粒，耗尽区的厚度与相互作用的排斥尾巴的范围相比，发生，在这个区域中的密度随着壁颗粒吸引力的强度增加而减小。在较大的分离，密度的指数阻尼振荡同意自组装系统的理论预测。大块的结构和热性能也被确定。特别是，一个新的结构交叉与比热的最大值，和双峰直方图的集群大小分布观察。
英文摘要：
Adsorption at an attractive surface in a system with particles self-assembling into small clusters is studied by Molecular dynamics (MD) simulation. We assume Lennard-Jones plus repulsive Yukawa tail interactions, and focus on small densities. The relative increase of the temperature at the critical cluster concentration near the attractive surface (CCCS) shows a power-law dependence on the strength of the wall-particle attraction. At temperatures below the CCCS, the adsorbed layer consists of undeformed clusters if the wall-particle attraction is not too strong. Above the CCCS, or for strong attraction leading to flattening of the adsorbed aggregates, we obtain a monolayer that for strong or very strong attraction consists of flattened clusters or stripes respectively. The accumulated repulsion from the particles adsorbed at the wall leads to a repulsive barrier that slows down the adsorption process, and the accession time grows rapidly with the strength of the wall-particle attraction. Beyond the adsorbed layer of particles, a depletion region of a thickness comparable with the range of the repulsive tail of interactions occurs, and the density in this region decreases with increasing strength of the wall-particle attraction. At larger separations, the exponentially damped oscillations of density agree with theoretical predictions for self-assembling systems. Structural and thermal properties of the bulk are also determined. In particular, a new structural crossover associated with the maximum of the specific heat, and a double-peaked histogram of the cluster size distribution are observed.
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