van der Waals Interaction between Rods: Analytical Description and Numerical Implementation*

An analytical description based on Hamaker theory has been derived for the van der Waals interaction between thin rods that can be approximated as lines of Lennard-Jones beads and between a rod and a Lennard-Jones bead. The description is implemented in LAMMPS, a widely used molecular simulator, to allow large-scale molecular dynamics simulations where rod-shaped objects are involved. The package is systematically tested and used to simulate the behavior of rods in a solvent modelled as a Lennard-Jones liquid. The simulation results reveal the anisotropic nature of the solvent-mediated rod-rod interaction in addition to the intrinsic anisotropic rod-rod interaction. Such interaction strongly affects the behavior of rods in the solvent under various flow conditions such as the alignment of rods in a shear flow. Evidence will also be presented on the isotropic-nematic transition in dense suspension of rods. The robust and flexible package will allow efficient computational studies of a wide range of rod-like systems, including liquid crystals, colloids, and filamentous materials such as carbon nanotubes and biological filaments.