  Hexagonal FeN monolayers on Cu(001) show a stripe pattern composed of dark
and bright stripes as observed recently by scanning tunneling microscopy (STM).
Here a harmonic mesh model is proposed to interpret those results. It uses a
planar Fourier analysis with two different wave vectors to calculate small
displacements of Fe atoms caused by lattice mismatch stress. The area of
displaced Fe atom triangles is used as a measure for the protrusion of N atoms
in their center. Proper selection of the wave vectors allows to visualize the
dominant protrusions of (Sqrt(3) x Sqrt(3)) ordered nitrogen atoms. The wave
vectors selected are related to Fe configurations which minimize lattice
mismatch stress. The model is kept simple, so just the most basic features of
the STM experiments are covered. The limits of the model are discussed and ways
for extending it are proposed.
