无定形聚乙烯热输运计算的全原子模型与联合原子模型的比较
Comparison of all atom and united atom models for thermal transport calculations of amorphous polyethylene
摘要：
聚合物模拟通常采用具有不同分子分辨率的模型。联合原子（UA）模型就是这样一个例子，其中分子中某些原子的基团聚集成超原子。虽然它们的计算简单性使它们特别有吸引力的研究范围广泛的聚合物的性能，在UA模型中的自由度的缺失可能会影响某些属性，是密切相关的局部振动，如热容量和热传输系数$κ$。相比之下，数值耗尽所有原子（AA）模型产生的结果更好地匹配实验数据。在这项工作中，我们系统地研究和比较$κ$获得的AA和UA模型的无定形聚乙烯系统。结果表明，UA描述可能不是一个合适的模型来评估热传输，因为它低估了$κ$相比，AA的描述和实验值。粗粒化导致较软的相互作用，并且其存在在UA模型的较弱机械响应中突出显示，因此也低估了$κ$。我们进一步巩固我们的研究结果，提取成键和非键的贡献$κ$的单链能量转移模型的框架内。
英文摘要：
Polymer simulations routinely employ models with different molecular resolutions. United atom (UA) models are one such example, where groups of certain atoms in a molecule are clustered into superatoms. Although their computational simplicity makes them particularly attractive for studying a wide range of polymer properties, the missing degrees of freedom in UA models can impact certain properties that are intimately linked to localized vibrations, such as the heat capacity and the thermal transport coefficient $κ$. In contrast, the numerically exhausting all atom (AA) models produce results that better match experimental data. In this work, we systematically investigate and compare $κ$ obtained from an AA and a UA models for an amorphous polyethylene system. The results indicate that the UA description may not be a suitable model for evaluating thermal transport, since it underestimates $κ$ in comparison to an AA description and the experimental value. The coarse-graining leads to the softer interactions and its presence is highlighted in a weaker mechanical response from the UA model, thus also underestimates $κ$. We further consolidate our findings by extracting the bonded and the nonbonded contributions to $κ$ within the framework of the single chain energy transfer model.
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