Van Hai Pham, Fortini Andrea, Schmidt Matthias
Theoretische Physik II, Physikalisches Institut, Universität Bayreuth, Universitätsstraße 30, D-95440 Bayreuth, Germany.
Department of Physics, Hanoi National University of Education, 136 Xuanthuy, Hanoi, Vietnam.
Phys Rev E. 2020 Jan;101(1-1):012608. doi: 10.1103/PhysRevE.101.012608.
A binary mixture of droplets and patchy colloids, where patches are arranged in tetrahedral symmetry, is studied with Metropolis Monte Carlo simulations. The colloidal patches attract droplets, while both the colloid-colloid and the droplet-droplet interactions are hard sphere like. We find stable crystal structures with atomic analogs ZnS, CaF_{2}, and fcc or hcp (face centered cubic or hexagonal close packed) of the droplets coexisting with a dispersed fluid of the colloids. The simulated crystal structures agree well with those predicted by close-packing calculations for an intermediate range of droplet-colloid size ratios. A discrepancy between the simulations and theoretical predictions occurs at low and high size ratios. The results of the simulations for mixtures with anisotropic colloid-droplet interactions reveal a richer phase diagram, with ZnS-gas and ZnS-fluid coexistence, as compared to the isotropic case. For the example of a square planar patch arrangement, we find a particular crystal structure, consisting of two interpenetrating fcc or hcp lattices with right bond angles. Such a structure has no known atomic analog. Our study of generic models of anisotropic colloid-droplet mixtures could provide a promising way towards the fabrication of novel and complex colloidal structures.
采用 metropolis 蒙特卡罗模拟研究了一种液滴与片状胶体的二元混合物，其中片状胶体呈四面体对称排列。胶体片吸引液滴，而胶体 - 胶体和液滴 - 液滴相互作用都类似于硬球相互作用。我们发现具有类似原子结构 ZnS、CaF₂ 以及液滴的面心立方（fcc）或六方密堆积（hcp）结构的稳定晶体结构与胶体的分散流体共存。对于中等范围的液滴 - 胶体尺寸比，模拟得到的晶体结构与密堆积计算预测的结构吻合良好。在低尺寸比和高尺寸比时，模拟结果与理论预测出现偏差。与各向同性情况相比，对具有各向异性胶体 - 液滴相互作用的混合物的模拟结果揭示了一个更丰富的相图，包括 ZnS - 气相和 ZnS - 流体共存。以方形平面片状排列为例，我们发现了一种特殊的晶体结构，它由两个具有直角键角的相互贯穿的 fcc 或 hcp 晶格组成。这种结构尚无已知的原子类似物。我们对各向异性胶体 - 液滴混合物通用模型的研究可能为制造新型复杂胶体结构提供一条有前景的途径。
