Nemd simulation to study viscosity of graphene filled polystyrene nanocomposites

In the present work, nonequilibrium molecular dynamics(NEMD) simulation was carried out to get an insight into the atomistic scale viscosity of graphene–polystyrene nanocomposite. The open access software Packmol was used to create amorphous PS and graphene+PS systems. The initial distribution of atoms in the two systems were created using cubic cells with periodic boundary conditions. Four pieces of graphene with side length of 5 nm x 5 nm and 400 polymeric chains consisting of three monomers per chain were randomly placed in the cubic cells to achieve a low concentration of graphene. The simulation box containing only PS was also created to provide a control. The simulations were conducted using LAMMPS with AIREBO potential and time step length of 1 fs. A Nose–Hoover style was selected to retain the system temperature. The SLLOD equations of motion were then applied to allow the system to undergo the flow under the NVT condition and mean square displacement (MSD), diffusion coefficient (D) and shear viscosity () were calculated.