npj: 胶体相分离动力学—FPD模拟

来源：知社学术圈

胶体悬浮液中的非平衡自组织包括一些基本的物理现象（如结晶），其相分离过程包括凝胶化和沉降。这些现象不仅对材料科学很重要，对认识活性物质和生物物质中的自组织也很重要。为解开这些非平衡现象背后的物理过程，人们非常希望用数值模拟方法来精确描述导致最终状态的动力学失衡过程。胶体和溶剂的运动是以动量守恒的复杂方式进行时空耦合，胶体颗粒之间的溶剂流体动力学相互作用（HI）又具有多体性，因此精确描述其物理过程是一项极具挑战性的任务。

来自东京大学工业科学研究所的Tanaka教授等人以包含液体的软材料为例，严格考查胶体相分离数值模拟的可预测性。使用粗粒度流体动力学（FPD）模拟，为含两种颗粒尺寸的胶体非平衡结构的演变建立了预测方法。他们通过对胶体势和温度(或热噪声)的精确匹配，再现了胶体相分离，几乎完美地再现了用三维共聚焦显微镜观察到的胶体结构和拓扑演化。但与此同时，最广泛使用的粗粒度方法布朗动力学(BD)模拟则完全不能重复这一过程。该研究证明了多体流体动力相互作用在胶体悬浮液动态结构形成中的基础性重要地位。更重要的是，这表明基于包括FPD模拟在内的Navier-Stokes方程直接计算的模拟方法对胶体悬浮液中的非平衡过程具有较高的预测能力，不仅有助于对软物质、生物质和活性物质的动力学行为和自组织的基本了解，而且有助于胶体材料的计算机辅助设计。

该文近期发表于npj Computational Materials 5: 40 (2019)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Numerical prediction of colloidal phase separation by direct computation of Navier–Stokes equation 

Michio Tateno & Hajime Tanaka 

Numerical prediction of out-of-equilibrium processes in soft and bio matter containing liquids is highly desirable. However, it is quite challenging primarily because the motions of the components at different hierarchical levels (e.g., large colloids and small solvent molecules) are spatio-temporally coupled in a complicated manner via momentum conservation. Here we critically examine the predictability of numerical simulations for colloidal phase separation as a prototype example of self-organization of soft materials containing a liquid. We use coarse-grained hydrodynamic simulations to tackle this problem, and succeed in almost perfectly reproducing the structural and topological evolution experimentally observed by three-dimensional confocal microscopy without any adjustable parameters. Furthermore, comparison with non-hydrodynamic simulations shows the fundamental importance of many-body hydrodynamic interactions in colloidal phase separation. The predictive power of our computational approach may significantly contribute to not only the basic understanding of the dynamical behavior and self-organization of soft, bio and active matter but also the computer-aided design of colloidal materials.