Computer Simulations of Structure, Dynamics, and Phase Behavior of Colloidal Fluids in Confined Geometry and under Shear (A05)

我们将研究两种受剪切变形影响的胶体体系，一种是约束下的胶体-聚合物混合物模型，另一种是形成玻璃的二元软球混合物。聚合物被描述为相互弱相互作用的软球体，而胶体-聚合物和胶体-胶体对与（排斥的）weeks -钱德勒-安德森势相互作用，因此胶体之间的耗尽吸引结果，类似于Asakura-Oosawa模型。将该系统限制在平行板之间，将用非平衡分子动力学研究相分离和剪切之间的相互作用，包括剪切对封闭界面上毛细波的抑制。还将考虑圆柱几何中的约束。通过粒子与汤川势的相互作用来描述玻璃化混合物，并通过lee - edwards边界条件实现剪切。瞬态时间相关现象的研究将扩展到振荡剪切系统和受恒定剪切应力影响的系统。后一个问题是微观流变模拟的宏观流变对应，从而能够阐明微观和宏观流变之间的关系。仿真结果将与模型耦合理论和实验结果进行比较。

Two types of colloidal systems exposed to shear deformation will be studied, a modelfor colloid-polymer mixtures under confinement, and a glass-forming binary soft spheremixture. Polymers are described as soft spheres weakly interacting with each other,while colloid-polymer and colloid-colloid pairs interact with the (repulsive) Weeks-Chandler-Andersen potential, so that a depletion attraction between colloids results,similar to the Asakura-Oosawa model. Confining this system between parallel plates,the interplay between phase separation and shear will be studied by Non-EquilibriumMolecular Dynamics, including the suppression of capillary waves at confined interfacesby the shear. Confinement in cylindrical geometry will also be considered. Theglass forming mixture is described by particles interacting with Yukawa potentials, andshear is implemented via Lees-Edwards boundary conditions. The study of transienttime-dependent phenomena will be extended to systems under oscillatory shear and tosystems that are subject to a constant shear stress. The latter problem is the macrorheologicalcounterpart to the micro-rheological simulation of a pulled probe particle,thus enabling to elucidate the relation between micro- and macro-rheology. The resultsof the simulation will be compared to those from mode-coupling theory and experiment.