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摘要运用经典分子动力学（MD）方法，模拟不同温度下单链聚乙烯势能及尺寸大小的变化和天然橡胶的力学性质。随着温度的升高，聚乙烯单链的总势能逐步升高，其价键伸缩振动能和键角弯曲能是决定系统总势能的主要因素。由范德华作用为主的非键能随温度升高，呈现先下降后升高的态势。使用均方末端距和回旋半径表征聚乙烯单链的尺寸变化，发现随着温度的升高，聚乙烯链团出现先收缩后扩张的趋势，其中在295K时尺寸最小。对天然橡胶的拉伸动力学模拟可以看到，在施加外部拉力时，能够得到其应力-应变曲线，屈服点出现明显。28090
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关键词 单链 聚乙烯 天然橡胶 势能 均方末端距 回旋半径 分子动力学模拟
毕业论文设计说明书外文摘要
Title A molecular dynamics simulation study of single molecular chain and natural rubber
Abstract
Classical molecular dynamics (MD) simulations were performed to study the potential energy and the size of a polyethylene molecular chain and the mechanical properties of natural rubber at different temperatures. With increasing temperatures, the total potential energy of a polyethylene molecular chain and the size of the chain gradually increased. Most parts of the potential were the contributions from the stretching vibration and bond angle vibration of the covalent bond. Nonbond energies, most of which were van der Waals energies, first decreased then increased, with increasing temperatures. The size of the single polyethylene molecular chain was characterized by mean square of end-to-end distance and radius of gyration. It was found it changed like parabolic curve with the minimized value at 295 K when the temperature was increasing. The stress-strain curves were obtained by tensile test simulations, in which yield points obviously appeared.
Key Words Molecular chain, Polyethylene, Natural rubber, Potential energy, Mean square end-to-end distance, Radius of gyration, Molecular dynamics simulation
目 次
摘要 I
Abstract II
1 绪论 1
1.1 研究背景及意义 1
1.2 聚乙烯 2
1.3 天然橡胶 2
1.4 研究方法 3
2 单链聚乙烯势能变化的模拟研究 4
2.1 引言 4
2.2 单链聚乙烯初始模型的构建 4
2.3 单链聚乙烯分子动力学模拟 5
2.3.1 力场选择 5
2.3.2 分子动力学模拟细节 5
2.4 结果与讨论 7
2.4.1 体系平衡判别 7
2.4.2 单链聚乙烯势能的细分 9
2.4.3 单链聚乙烯势能项随温度的变化规律 11
2.5 本章小结 14
3 单链聚乙烯尺寸的模拟研究 15
3.1 引言 15
3.2 单链聚乙烯的均方末端距分析 15
3.3 单链聚乙烯的回旋半径分析 17
3.4 结果与讨论 19
3.4.1 单链聚乙烯均方末端距随温度变化规律 19
3.4.2 单链聚乙烯回旋半径随温度变化规律 20
3.5 本章小结 22
4 天然橡胶的拉伸试验分子动力学模拟 24
4.1 引言 24
4.2 天然橡胶高分子链模型的构建 24