Two-step crystallization and solid-solid transitions in binary colloidal mixtures.
Two-step crystallization and solid-solid transitions in binary colloidal mixtures.
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DOI：
10.1073/pnas.2008561117
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发表时间：
2020-11-10
影响因子：
11.1
通讯作者：
Rogers WB
中科院分区：
文献类型：
--
作者：
Fang H;Hagan MF;Rogers WB
结晶——从无序的流体中自发形成有序的固体——几个世纪以来一直吸引着人类。长期以来的理论预测晶体是由单一成核事件形成的，而最近的实验表明，结晶可以跨越多个中间态。在本文中，我们观察到一个两步结晶途径，首先形成一个亚稳晶体，然后转变成另一个具有不同晶体学对称性的晶体。这种转变是无扩散的：粒子经历连贯的局部重排。利用互补的计算机模拟，我们表明两步结晶途径是由相互竞争的热力学力驱动的，因此，在许多物理系统中可能是共同的。结晶是材料科学的基础，也是各种应用的核心，从微电子硅晶片的制造到蛋白质结构的测定。基本原理是，晶体是由均匀流体自发涨落形成的，这种涨落使系统越过单一的自由能势垒。然而，越来越明显的是，成核往往比这个简单的图更复杂，相反，可以通过亚稳结构沿着热力学最小值的路径进行多次转变。在本文中，我们观察，表征，并利用dna包被胶体的结晶途径模型。我们使用光学显微镜，以单粒子分辨率研究二元胶体混合物的结晶。我们观察到经典的一步途径和非经典的两步途径，通过晶体中间体的固-固转变进行。我们还使用增强采样来计算与我们的实验相对应的自由能景观，并表明一步和两步路径都是由热力学单独驱动的。具体来说，两步固-固转变是由两种不同晶体相之间的竞争控制的，自由能取决于晶体尺寸。这些结果扩展了我们对可用的结晶途径的理解，通过表明大小相关的热力学力可以产生具有多个晶体相的途径，这些晶体相可以在没有自由能垒的情况下相互转换，并且可以提供控制由胶体制成的材料的自组装的方法。
Crystallization—the spontaneous formation of an ordered solid from a disordered fluid—has fascinated humankind for centuries. Contrary to longstanding theories, which predict that crystals form by a single nucleation event, recent experiments have shown that crystallization can traverse multiple intermediate states. In this paper, we observe a two-step crystallization pathway, in which a metastable crystal forms first and later transforms into another crystal with a different crystallographic symmetry. This transformation is diffusionless: The particles undergo coherent, local rearrangements. Using complementary computer simulations, we show that the two-step crystallization pathway is driven by competing thermodynamic forces and, thus, could be common to many physical systems. Crystallization is fundamental to materials science and is central to a variety of applications, ranging from the fabrication of silicon wafers for microelectronics to the determination of protein structures. The basic picture is that a crystal nucleates from a homogeneous fluid by a spontaneous fluctuation that kicks the system over a single free-energy barrier. However, it is becoming apparent that nucleation is often more complicated than this simple picture and, instead, can proceed via multiple transformations of metastable structures along the pathway to the thermodynamic minimum. In this article, we observe, characterize, and model crystallization pathways using DNA-coated colloids. We use optical microscopy to investigate the crystallization of a binary colloidal mixture with single-particle resolution. We observe classical one-step pathways and nonclassical two-step pathways that proceed via a solid–solid transformation of a crystal intermediate. We also use enhanced sampling to compute the free-energy landscapes corresponding to our experiments and show that both one- and two-step pathways are driven by thermodynamics alone. Specifically, the two-step solid–solid transition is governed by a competition between two different crystal phases with free energies that depend on the crystal size. These results extend our understanding of available pathways to crystallization, by showing that size-dependent thermodynamic forces can produce pathways with multiple crystal phases that interconvert without free-energy barriers and could provide approaches to controlling the self-assembly of materials made from colloids.
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影响因子：
3.4
作者：
Mahynski NA;Zerze H;Hatch HW;Shen VK;Mittal J
通讯作者：
Mittal J
DOI：
10.1016/0001-6160(62)90185-2
发表时间：
1962-01-01
期刊：
ACTA METALLURGICA
影响因子：
--
作者：
GILBERT, A;OWEN, WS
通讯作者：
OWEN, WS
影响因子：
15
作者：
Pauling, L
通讯作者：
Pauling, L
DOI：
10.1073/pnas.1109853108
发表时间：
2011-09-20
影响因子：
11.1
作者：
Rogers, W. Benjamin;Crocker, John C.
通讯作者：
Crocker, John C.
DOI：
10.1073/pnas.110000497
发表时间：
2000-06-06
影响因子：
11.1
作者：
Galkin, O;Vekilov, PG
通讯作者：
Vekilov, PG