We carried out large-scale atomistic molecular dynamics simulations to study the growth of twin lamellar crystals of polyethylene initiated by small crystal seeds. By examining the size distribution of the stems-straight crystalline polymer segments-we show that the crystal edge has a parabolic profile. At the growth front, there is a layer of stems too short to be stable, and new stable stems are formed within this layer, leading to crystal growth. Away from the edge, the lengthening of the stems is limited by a lack of available slack length in the chains. This frustration can be relieved by mobile crystal defects that allow topological relaxation by traversing through the crystal. The results shed light on the process of polymer crystal growth and help explain initial thickness selection and lamellar thickening.

中文翻译：

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通过分子动力学研究聚乙烯晶体生长：晶体边缘和层状厚度。

我们进行了大规模原子分子动力学模拟，以研究由小晶种引发的聚乙烯孪晶层状晶体的生长。通过检查茎（直结晶聚合物链段）的尺寸分布，我们发现晶体边缘具有抛物线轮廓。在生长前沿，有一层茎太短而不稳定，并且在该层内形成新的稳定茎，导致晶体生长。远离边缘，茎的加长受到链条中缺乏可用松弛长度的限制。这种挫败感可以通过移动晶体缺陷来缓解，这些缺陷可以通过穿过晶体来实现拓扑弛豫。这些结果揭示了聚合物晶体生长的过程，并有助于解释初始厚度选择和层状增厚。