Formation of a crystal nucleus from liquid
Formation of a crystal nucleus from liquid
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DOI：
10.1073/pnas.1001040107
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发表时间：
2010-08-10
影响因子：
11.1
通讯作者：
Tanaka, Hajime
中科院分区：
文献类型：
--
作者：
Kawasaki, Takeshi;Tanaka, Hajime
结晶是各种材料普遍存在的最基本的非平衡现象之一。到目前为止，人们一直认为过冷液体在结晶前处于“均匀无序状态”。与这一普遍看法相反，我们揭示了过冷胶体液体实际上不是均匀的，而是具有瞬变的中期结构有序性。通过润湿效应，我们发现晶核优先发生在结构有序度较高的区域，从而显著降低了晶液界面能，从而促进了晶体的成核。这一新颖的情景为解决一个长期存在的谜团提供了线索，这个谜团涉及基于经典成核理论的成核率的严格数值估计与实验观察到的成核率之间的巨大差异。我们的发现不仅可以揭示晶体成核的机制，还可以揭示过冷液态的基本性质。
Crystallization is one of the most fundamental nonequilibrium phenomena universal to a variety of materials. It has so far been assumed that a supercooled liquid is in a "homogeneous disordered state" before crystallization. Contrary to this common belief, we reveal that a supercooled colloidal liquid is actually not homogeneous, but has transient medium-range structural order. We find that nucleation preferentially takes place in regions of high structural order via wetting effects, which reduce the crystal-liquid interfacial energy significantly and thus promotes crystal nucleation. This novel scenario provides a clue to solving a long-standing mystery concerning a large discrepancy between the rigorous numerical estimation of the nucleation rate on the basis of the classical nucleation theory and the experimentally observed ones. Our finding may shed light not only on the mechanism of crystal nucleation, but also on the fundamental nature of a supercooled liquid state.