Scale-bridging phase-field simulations of microstructure responses on nucleation in metals and colloids

从原子到介观尺度的相场模拟被用来分析金属和胶体体系中异质形核的微观结构响应。通过结合分子动力学（MD）和相场（PF）模拟或混合PF模拟实现了金属中从1 nm到10 μm的尺度桥接。三维数值计算的关键是采用性能优化的模拟技术和自适应网格。热力学参数Ni，Ni-Cu，Ti，Al-Cu，Al-Ni和Al-Ti提供从实验测量以及从MD模拟的合作基团。在PF模拟中，系统地研究了微结构对参数集、晶核形状和衬底特性的响应。大规模的模拟微观结构的形成与实验观察进行了比较。PF模型的扩展涵盖了一种方法，将体积约束，线张力能量制剂和特定的边界条件在基板的表面。新模型应用于座滴模拟，以精确分析平衡形状和扩散过程。特别是，高阶势的形式主义被用来调查的长度尺度依赖的影响的线张力的杨氏力平衡在三维三线。在最近设计的PF晶体模型的基础上，提出了一个新的硬球胶体体系的PF模型。Ginzburg-Landau泛函将从动态密度泛函理论（DDFT）中推导出，并考虑到Forware通量采样（FFS）相关序参数的识别结果。

Phase-field simulations from atomic to mesoscopic length scales are used to analyse the microstructure responses on heterogeneous nucleation, both in metallic as well as in colloidal systems. The scale-bridging from 1 nm to 10 μm in metals is achieved either by combining Molecular Dynamics (MD) and Phase-field (PF) simulations or by hybrid PF modelling. Essential for three dimensional numerical computations is the employment of performance optimized simulation techniques and adaptive grids. Thermodynamic parameters for Ni, Ni-Cu, Ti, Al-Cu, Al-Ni and Al-Ti are provided from experimental measurements as well as from MD simulations of cooperating groups. The microstructure responses on the parameter sets, on the shape of the nuclei and on the characteristic properties of the substrate are systematically investigated in PF simulations. Large-scale simulations of microstructure formations are compared with experimental observations. Extensions of the PF model cover a method to incorporate volume constraints, a line tension energy formulation and specific boundary conditions at the surface of the substrate. The new model is applied to sessile drop simulations to precisely analyse equilibrium shapes and diffusion processes. In particular, the formalism with higher order potentials is used to investigate the length-scale dependent effect of the line tension on the Young’s force balance at triple lines in 3D. A new PF model for colloidal systems of hard spheres will be formulated on the basis of the recently designed PF crystal model. The Ginzburg-Landau functional will be derived from Dynamical Density Functional Theory (DDFT) taking the results from identification of the order parameter of relevance from Forware Flux Sampling (FFS) into account.