Abstract
In this chapter, we present a method for the prescription of periodic boundary conditions in DEM simulations of granular materials. This method is similar in practice to that of Parrinello and Rahman, but since the particle interactions are dissipative in a granular system, the equations of motion for collective dynamic variables can not be based on a Hamiltonian. We consider in detail the particular kinematics of periodic systems, the equations of dynamics and time-stepping schemes for MD-DEM and CD-DEM.