  We have studied the reconstruction of Pt(111) theoretically using a
two-dimensional Frenkel-Kontorova model for which all parameters have been
obtained from ab initio calculations. We find that the unreconstructed surface
lies right at the stability boundary, and thus it is relatively easy to induce
the surface to reconstruct into a pattern of FCC and HCP domains, as has been
shown experimentally. The top layer is very slightly rotated relative to the
substrate, resulting in the formation of "rotors" at intersections of domain
walls. The size and shape of domains is very sensitive to the density in the
top layer, the chemical potential, and the angle of rotation, with a smooth and
continuous transition from the honeycomb pattern to a Moire pattern, via
interlocking triangles and bright stars. Our results show clearly that the
domain patterns found on several close-packed metal surfaces are related and
topologically equivalent.
