  The isotropic-to-nematic transition in liquid crystals is studied in d=3
spatial dimensions. A simulation method is proposed to measure the angle
dependent interfacial tension g(theta), with theta the anchoring angle of the
nematic phase at the interface. In addition, an alternative liquid crystal
model is introduced, defined on a lattice. The advantage of the lattice model
is that accurate simulations of anchoring effects become possible. For the
lattice model, g(theta) depends sensitively on the nearest-neighbor pair
interaction, and both stable and metastable anchoring angles can be detected.
We also measure g(theta) for an off-lattice fluid of soft rods. For soft rods,
only one stable anchoring angle is found, corresponding to homogeneous
alignment of the nematic director in the plane of the interface. This finding
is in agreement with most theoretical predictions obtained for hard rods.
