  Coexistence between the isotropic and the nematic phase in suspensions of
rods is studied using grand canonical Monte Carlo simulations with a bias on
the nematic order parameter. The biasing scheme makes it possible to estimate
the interfacial tension gamma in systems of hard and soft rods. For hard rods
with L/D=15, we obtain gamma ~ 1.4 kB T/L^2, with L the rod length, D the rod
diameter, T the temperature, and kB the Boltzmann constant. This estimate is in
good agreement with theoretical predictions, and the order of magnitude is
consistent with experiments.
