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本文基于位置有序参数(SOP)分析了利用图形处理器(GPU)加速的分子动力学程序GMD模拟含有4.5万和36万个CH2联合原子的聚乙烯纳米球的分子动力学结晶过程中结晶度的变化,并使用Avrami方程得到了不同温度下的结晶指数.与一般实验结果相同,该指数n不为整数.我们提出了二元混合模型,认为纳米线团的结晶行为由两种机理按一定比例组成.当结晶温度升高时,两种尺寸的纳米线团的Avrami指数均升高并接近4,结晶机理趋向三维生长和均相成核.当温度低时,晶核多在接近纳米球的表面生成,Avrami指数趋近于1.我们对体系结晶成核阶段结束时晶核沿纳米球的径向分布进行了分析.结果表明Tn=0.60时晶核的生成位置接近表面,而Tn=0.68时晶核出现一个接近纳米球内部的峰.该结果与二元混合模型的Avrami指数的分析结果相吻合.
In this paper, we analyzed the molecular dynamics simulation of a polyethylene nanosphere containing 45,000 and 360,000 CH2 co-atoms using the molecular dynamics simulations accelerated by a GPU (GPU) based on the positional order parameter (SOP) And the Avrami equation was used to obtain the crystallinity index at different temperatures.As with the general experimental results, the index n is not an integer.We propose a binary mixed model that the crystallization behavior of nanowire clusters by both mechanisms according to a certain As the crystallization temperature increases, the Avrami index of the nanowire clusters of both sizes increases and approaches 4, and the crystallization mechanism tends to three-dimensional growth and homogeneous nucleation.When the temperature is low, the nuclei are close to the nanosphere The Avrami index approaches 1. The radial distribution of nuclei along the nanospheres at the end of the nucleation stage of the system is analyzed.The results show that the nuclei are generated near the surface with Tn = At 0.68, the nuclei showed a peak near the interior of the nanospheres, which agrees with the analysis of the Avrami index of the binary mixed model.