  We present Monte Carlo simulation results for a two-dimensional Ising model
with ferromagnetic nearest-neighbor couplings and a competing long-range
dipolar interaction on a honeycomb lattice. Both structural and thermodynamic
properties are very similar to the case of a square lattice, with the exception
that structures reflect the sixfold rotational symmetry of the underlying
honeycomb lattice. To deal with the long-range nature of the dipolar
interaction we also present a simple method of evaluating effective interaction
coefficients, which can be regarded as a more straightforward alternative to
the prevalent Ewald summation techniques.
