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首页> 外文期刊>Computer physics communications >Coding coarse grained polymer model for LAMMPS and its application to polymer crystallization
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Coding coarse grained polymer model for LAMMPS and its application to polymer crystallization

机译：LAMMPS的粗粒聚合物编码模型及其在聚合物结晶中的应用

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We present a patch code for LAMMPS to implement a coarse grained (CG) model of poly(vinyl alcohol) (PVA). LAMMPS is a powerful molecular dynamics (MD) simulator developed at Sandia National Laboratories. Our patch code implements tabulated angular potential and Lennard-jones-9-6 (LJ96) style interaction for PVA. Benefited from the excellent parallel efficiency of LAMMPS, our patch code is suitable for large-scale simulations. This CG-PVA code is used to study polymer crystallization, which is a long-standing unsolved problem in polymer physics. By using parallel computing, cooling and heating processes for long chains are simulated. The results show that chain-folded structures resembling the lamellae of polymer crystals are formed during the cooling process. The evolution of the static structure factor during the crystallization transition indicates that long-range density order appears before local crystalline packing. This is consistent with some experimental observations by small/wide angle X-ray scattering (SAXS/WAXS). During the heating process, it is found that the crystalline regions are still growing until they are fully melted, which can be confirmed by the evolution both of the static structure factor and average stem length formed by the chains. This two-stage behavior indicates that melting of polymer crystals is far from thermodynamic equilibrium. Our results concur with various experiments. It is the first time that such growth/reorganization behavior is clearly observed by MD simulations. Our code can be easily used to model other type of polymers by providing a file containing the tabulated angle potential data and a set of appropriate parameters.
机译：我们为LAMMPS提供了一个补丁代码，以实现聚乙烯醇（PVA）的粗粒（CG）模型。 LAMMPS是由Sandia国家实验室开发的功能强大的分子动力学（MD）仿真器。我们的补丁代码为PVA实现了表格化的角势和Lennard-jones-9-6（LJ96）样式的交互。得益于LAMMPS的出色并行效率，我们的补丁代码适用于大规模仿真。此CG-PVA代码用于研究聚合物结晶，这是聚合物物理学中一个长期未解决的问题。通过使用并行计算，模拟了长链的冷却和加热过程。结果表明，在冷却过程中形成了类似于聚合物晶体薄片的链折叠结构。结晶转变过程中静态结构因子的演变表明，在局部晶体堆积之前出现了远距离密度阶。这与小/广角X射线散射（SAXS / WAXS）的一些实验观察结果一致。在加热过程中，发现结晶区域仍在生长直到完全熔化为止，这可以通过链形成的静态结构因子和平均茎长的演变来证实。这种两阶段行为表明，聚合物晶体的熔融远没有达到热力学平衡。我们的结果与各种实验一致。这是第一次通过MD模拟清楚地观察到这种生长/重组行为。通过提供包含列表角势数据和一组适当参数的文件，我们的代码可轻松用于建模其他类型的聚合物。

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