Amorphous Precursors in the Nucleation of Clathrate Hydrates
Amorphous Precursors in the Nucleation of Clathrate Hydrates
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DOI：
10.1021/ja1051445
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发表时间：
2010-08-25
影响因子：
15
通讯作者：
Molinero, Valeria
中科院分区：
文献类型：
--
作者：
Jacobson, Liam C.;Hujo, Waldemar;Molinero, Valeria
用两相体系的分子动力学模拟方法研究了与甲烷或二氧化碳相当的疏水客体的笼状水合物的成核和生长过程。结晶过程分两步进行：第一步，客体分子集中在“团块”中，即无定形的团簇，涉及水介导型的多个客体分子。这些斑点与稀溶液处于动态平衡状态，并产生笼状笼子，最终将其转变为无定形笼状核。在第二步中，无定形笼状物转变为晶状笼状物。在低温下，体系可以在亚稳的无定形笼状物相中停留足够长的时间，使其在笼状物的结晶过程中表现为中间体。这项工作揭示的“斑点机制”综合了不稳定团簇的元素和笼状成核的局部结构假说，与蛋白质和胶体结晶的两步机制有很强的相似性。
The nucleation and growth of clathrate hydrates of a hydrophobic guest comparable to methane or carbon dioxide are studied by molecular dynamics simulations of two-phase systems. The crystallization proceeds in two steps: First, the guest molecules concentrate in "blobs", amorphous clusters involving multiple guest molecules in water-mediated configurations. These blobs are in dynamic equilibrium with the dilute solution and give birth to the clathrate cages that eventually transform it into an amorphous clathrate nucleus. In a second step, the amorphous clathrate transforms into crystalline clathrate. At low temperatures, the system can be arrested in the metastable amorphous clathrate phase for times sufficiently long for it to appear as an intermediate in the crystallization of clathrates. The "blob mechanism" unveiled in this work synthesizes elements of the labile cluster and local structuring hypotheses of clathrate nucleation and bears strong analogies to the two-step mechanisms of crystallization of proteins and colloids.