Multi-sphere rigid-body particles in a parallelized LEBC with LIGGGHTS

A method for the Message Passing Interface (MPI) parallelization of the Lees-Edwards boundary condition (LEBC) within the LIGGGHTS framework for multi-sphere rigid particles was created, allowing for the simulation of very detailed complex shapes. Double-send and double-receive communication was added to LIGGGHTS to allow for shared information across disjointed processor domains along the shearing boundary of the LEBC. The verification of this method is performed via 3D shearing simulations of single spheres and sphere clumps and rods with aspect ratios 2, 4, and 6. The predicted shear stress employing the new parallelized LEBC method matches stress values from granular kinetic theory and previously published simulation results. No LEBC simulations for DEM or multi-sphere rigid particles are known to be parallelized, allowing for computationally difficult LEBC multi-sphere simulations to be performed for the first time.