  Using molecular dynamics (MD) simulations we study the interactions between
elongated colloidal particles (length to breath ratio > 1) in a nematic host.
The simulation results are compared to the results of a Landau-de Gennes
elastic free energy. We find that depletion forces dominate for the sizes of
the colloidal particles studied. The tangential component of the force,
however, allows us to resolve the elastic contribution to the total
interaction. We find that this contribution differs from the quadrupolar
interaction predicted at large separations. The difference is due to the
presence of nonlinear effects, namely th e change in the positions and
structure of the defects and their annihilation at small separations.
