Kinetics and Thermodynamics of the Self-Assembly of Polyhedral Nano-Colloids into Pure and Mixed Crystals

PI：Ecobedo，Fernando A.建议编号：1403118机构：康奈尔大学标题：多面体纳米胶体自组装成纯晶体和混合晶体的动力学和热力学多面体纳米粒子(NPs)可以组装成超晶格材料，有可能形成具有巨大不同光学、电子、物理和化学性质的相。这项建议是在过去成功的基础上提出的，将侧重于了解相、中间相和晶体之间转变的动力学。这种动力学在这些结构的实验实现中起着至关重要的作用，所获得的见解将使人们能够找到催化自组装过程的方法，或者设计出将系统引导到理想阶段的方法。从长远来看，这样的结果可能会对陶瓷、塑料和半导体行业产生影响，因为它有助于拓宽可用于开发稳定的纳米复合材料、液态装甲、用于光子材料的胶体介晶和用于光伏的纳米晶体阵列的方法。先进的蒙特卡罗(例如，Gibbs-Duem与半宏正则系综积分)和分子动力学模拟将被用于研究不同体积分数的硬(或方井吸引)形状是如何组织的。对于这样的系统，很容易在实验中陷入动力学陷阱(无论是作为想要的结构还是不想要的结构)，因此了解非常重要的是，不仅要了解平衡状态，而且要了解动力学，这是这里的重点。在这种情况下，形成的中间相可以提供中间态，从而降低无序状态和结晶态之间原本很高的能垒。这些研究不仅包括纯体系(包含一种类型的多面体粒子)，还包括二元混合物中相变的热力学和动力学。要研究的粒子包括可以在实验中产生的多面体(立方体、立方八面体、截断八面体和八面体)，以及这些粒子的混合物(也包括球形粒子)。模拟将模拟混合物的热力学行为，并将使用新的序参数和正向通量采样方法的变量来模拟相变的动力学。

PI: Escobedo, Fernando A.Proposal Number: 1403118Institution: Cornell UniversityTitle: Kinetics and Thermodynamics of the Self-Assembly of Polyhedral Nano-Colloids into Pure and Mixed CrystalsPolyhedral nanoparticles (NPs) can be assembled into super-lattice materials that has the potential to form phases exhibiting vastly different optical, electronic, physical, and chemical properties. This proposal, building on past successes, will focus on understanding the kinetics of the transitions between phases, mesophases, and crystals. Such kinetics play a crucial role in the experimental realization of these structures and the insights gained would allow ways to catalyze the self-assembly process, or design ways to steer the systems into desirable phases. In the long term, such results could have an impact on the ceramic, plastics, and semiconductor industries by helping broaden the approaches available to develop stable nanocomposites, liquid armors, colloid-based mesocrystals for photonic materials, and nanocrystal arrays for photovoltaics.Advanced Monte Carlo (e.g., Gibbs-Duhem integration with semi-grand canonical ensembles) and Molecular Dynamics simulations will be used to study how hard (or square-well attraction) shapes organize at different volume fractions. For such systems, it's easy to become kinetically trapped experimentally (either as a desired or undesired structure), so it's very important to understand, not just the equilibrium state, but the kinetics, which is the focus here. In this context, the mesophases that are formed may provide intermediate states that lower the otherwise high energy barrier between disordered and crystalline states. The investigations will include not just pure systems (containing one type of polyhedral particles), but also the thermodynamics and kinetics of phase transitions in binary mixtures. Particles to be investigated include polyhedra that can be produced in experiments (cubes, cuboctahedra, truncated octahedra, and octahedra), and mixtures of those (including also spherical particles). The simulations will model the thermodynamic behavior of the mixtures, and new order parameters and variants of the forward flux sampling method will be used to simulate the kinetics of phase transitions.