基于第一性原理的统一原子力场预测定向聚乙炔的极高热导率
Extremely High Thermal Conductivity of Aligned Polyacetylene Predicted using First-Principles-Informed United-Atom Force Field
摘要：
聚合物的分子模拟依赖于精确的力场来描述原子间的相互作用。在这项工作中，我们使用第一性原理密度泛函理论（DFT）计算参数化的聚乙炔（PA），一个共轭聚合物的潜在的高热导率的联合原子力场。对DFT中不同的电子相关泛函进行了测试。明确描述了共轭聚合物主链中交替的单键和双键的键合相互作用，并分别对II类非谐函数进行了参数化。键角和二面角的相互作用也是非谐的，并对DFT能量表面参数化。利用所建立的力场进行分子动力学（MD）模拟，计算了PA单链和不同模拟畴长的PA晶体的热导率。结果表明，PA分子链和晶体的热导率都很高，且具有长度依赖性。在790 nm处，它们各自的热导率值为~480 Wm-1 K-1和~320 Wm-1 K-1，这相对高于聚乙烯（PE）的热导率，聚乙烯是迄今为止测量的最导热的聚合物纤维。
英文摘要：
Molecular simulations of polymer rely on accurate force fields to describe the inter-atomic interactions. In this work, we use first-principles density functional theory (DFT) calculations to parameterize a united-atom force field for polyacetylene (PA), a conjugated polymer potentially of high thermal conductivity. Different electron correlation functionals in DFT have been tested. Bonding interactions for the alternating single and double bonds in the conjugated polymer backbone are explicitly described and Class II anharmonic functions are separately parameterized. Bond angle and dihedral interactions are also anharmonic and parameterized against DFT energy surfaces. The established force field is then used in molecular dynamics (MD) simulations to calculate the thermal conductivity of single PA chains and PA crystals with different simulation domain lengths. It is found that the thermal conductivity values of both PA single chains and crystals are very high and are length-dependent. At 790 nm, their respective thermal conductivity values are ~480 Wm-1K-1 and ~320 Wm-1K-1, which are comparatively higher than those of polyethylene (PE), the most thermally conductive polymer fiber measured up-to-date.
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