  We have derived exact expressions for the domain wall free energy along the
three high-symmetry directions of a triangular lattice with anisotropic
nearest-neighbor interactions. The triangular lattice undergoes an
orderdisorder phase transition at a temperature Tc given by exp(-(e1+e2)/2kTc)+
exp(-(e2+e3)/2kTc)+ exp(-(e3+e1)/2kTc)= 1, where e1, e2, e3 are the
nearest-neighbor interaction energies, and e1+ e2> 0, e2+ e3> 0, e3+ e1> 0.
Finally, we have derived expressions for the thermally induced meandering of
the domain walls at temperatures below the phase transition temperature. We
show how these expressions can be used to extract the interaction energies of
two-dimensional systems with a triangular lattice.
