Mechanisms of Nucleation and Solid-Solid-Phase Transitions in Triblock Janus Assemblies
Mechanisms of Nucleation and Solid-Solid-Phase Transitions in Triblock Janus Assemblies
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DOI：
10.1021/acs.jctc.0c01080
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发表时间：
2021-02-02
影响因子：
5.5
通讯作者：
Mueller-Plathe, Florian
中科院分区：
文献类型：
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作者：
Eslami, Hossein;Gharibi, Ali;Mueller-Plathe, Florian
一个模型，包括核心纳米粒子的化学细节，以及明确的表面电荷和疏水补丁，三块Janus粒子模拟成核和固-固相变在二维层。该模型包括显式溶剂和基质，并在多体耗散粒子动力学模拟中考虑了流体动力学和多体相互作用。为了不强加先验机制，我们进行了自由（无偏）模拟，让系统自由选择自己的路径。与实验和先前有偏见的模拟一致，检测到一个两步机制的kagome晶格从溶液中的成核。然而，本无偏与有偏模拟的一个明显特点是，多个核出现的解决方案，在他们的成长，在晶界的对齐和错位的小平面被引入到系统中。被困在相邻原子核之间的液体状粒子将它们连接在一起。相邻原子核的对称面不匹配会阻碍不太稳定（较小）原子核的生长。这种核在未对准的刻面的晶界处的统一遵循两步机制：较小的核的熔化，随后在较大的相邻核的界面处的液体状颗粒的后续成核。此外，在模拟箱中形成了多个后临界核，其中一些核的生长由于在系统中引入应变而停止。这种不完全的成核/生长机制与最近的实验完全一致。在弱过热下，固-固（六边形到果粒）相变遵循两步机制：较慢的步骤（形成液滴），然后是较快的步骤（从液滴成核果粒）。
A model, including the chemical details of core nanoparticles as well as explicit surface charges and hydrophobic patches, of triblock Janus particles is employed to simulate nucleation and solid-solid phase transitions in two-dimensional layers. An explicit solvent and a substrate are included in the model, and hydrodynamic and many-body interactions were taken into account within many-body dissipative particle dynamics simulation. In order not to impose a mechanism a priori, we performed free (unbiased) simulations, leaving the system the freedom to choose its own pathways. In agreement with the experiment and previous biased simulations, a two-step mechanism for the nucleation of a kagome lattice from solution was detected. However, a distinct feature of the present unbiased versus biased simulations is that multiple nuclei emerge from the solution; upon their growth, the aligned and misaligned facets at the grain boundaries are introduced into the system. The liquid-like particles trapped between the neighboring nuclei connect them together. A mismatch in the symmetry planes of neighboring nuclei hinders the growth of less stable (smaller) nuclei. Unification of such nuclei at the grain boundaries of misaligned facets obeys a two-step mechanism: melting of the smaller nuclei, followed by subsequent nucleation of liquid-like particles at the interface of bigger neighboring nuclei. Besides, multiple postcritical nuclei are formed in the simulation box; the growth of some of which stops due to introduction of a strain in the system. Such an incomplete nucleation/growth mechanism is in complete agreement with the recent experiments. The solid-solid (hexagonal-to-kagome) phase transition, at weak superheatings, obeys a two-step mechanism: a slower step (formation of a liquid droplet), followed by a faster step (nucleation of kagome from the liquid droplet).