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，另一种是玻璃形成的二元软球混合物。聚合物被描述为彼此弱相互作用的软球，而胶体-聚合物和胶体-胶体对与(排斥性)Week-Chandler-Andersen势相互作用，从而导致胶体之间的耗尽吸引，类似于浅仓-小泽模型。将这一体系限制在平行板之间，用非平衡分子动力学研究相分离与剪切之间的相互作用，包括剪切对受限界面毛细管波的抑制。柱面几何中的约束也将被考虑。玻璃形成的混合物用粒子与Yukawa势相互作用来描述，剪切用Lees-Edwards边界条件实现。对瞬变时间相关现象的研究将扩展到振荡剪切下的系统和承受恒定剪应力的系统。后一个问题是与拉动探针颗粒的微观流变学模拟相对应的宏观流变学，从而能够阐明微观和宏观流变学之间的关系。将模拟结果与模式耦合理论和实验结果进行了比较。

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.