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.