模拟聚乙烯块体相变和导热的粗粒化模型和势场建立

Coarse-grained model and force field development for predicting phase change and thermal transport in polyethylene

建立适用于介观尺度聚乙烯块体相变和导热分子模拟的粗粒化模型及势场,并对其进行验证。基于全原子分子动力学模拟结果,采用多态-迭代玻尔兹曼变换法进行粗粒化分子动力学模拟来获得粗粒化势场。结果表明:粗粒化势场采用函数形式的势能描述,易于使用;对比全原子模拟结果,粗粒化势场能够较准确地模拟聚乙烯块体的静态结构性质;聚乙烯块体在300 K和500 K下密度的模拟值与实验值误差小于3%,玻璃化转变温度和熔化温度的模拟值与实验值相符较好;单链聚乙烯导热系数的粗粒化势场模拟值与全原子模拟值较一致,无序聚乙烯块体导热系数的模拟值与实验值吻合较好。研究结果为介观尺度聚乙烯的导热研究提供了一种更高效的模拟方法。

Coarse-grained model and force field for predicting phase change and thermal transport in meso-scale polyethylene were developed and its accuracy was validated.The coarse-grained force field was obtained through coarse-grained molecular dynamics simulations by multistate iterative Boltzmann inversion with all-atom molecular dynamics simulations as a benchmark.The simulations results show that the coarse-grained force field consisting of functional potential terms allows better transferability and more accurate description of the static structural properties of bulk polyethylene compared with those in all-atom simulations.Meanwhile,the deviations between values in coarse-grained simulations and experimental results of densities of bulk polyethylene at 300 K and 500 K are both within 3%.The values of glass transition temperature and melting temperature obtained from coarse-grained simulation are both close to experimental values.In addition,thermal conductivities of extended single polyethylene chain with various lengths in coarse-grained simulations match those in all-atom simulations well and thermal conductivity of disordered bulk polyethylene in coarse-grained simulation is close to the experimental value.The results provide a more powerful simulation method for the investigation of thermal conduction of meso-scale polyethylene.