Molecular dynamics simulation of diffusion of hydrogen and its isotopic molecule in polystyrene

Polystyrene is one of the target materials used in Inertial Confinement Fusion (ICF). Molecular dynamics simulations are performed in this report to study the diffusion of gases, including hydrogen and its isotopic molecule under normal temperature and pressure. According to the Mean Square Displacement (MSD) of the gas moving in polystyrene, the diffusion coefficient of hydrogen, deuterium and tritium in different molecular weight polystyrene were obtained. The calculated diffusion coefficients agree well with the results of former simulation studies. The diffusion coefficients of polystyrene of the same molecular weight gradually decrease along with the increase of mass fraction of hydrogen isotopes (hydrogen, deuterium and tritium). The study also finds that diffusion coefficients will decrease along with the increasing of polystyrene molecular weight. Moreover, the pair correlation functions, cohesive energy density and fractional free volume were studied corresponding to hydrogen isotopes diffusion coefficients.