We perform detailed numerical simulations of field ion microscopy images of faceted crystals and compare them with experimental observations. In contrast to the case of crystals with a smooth surface, for a faceted topography we find extreme deformations of the ion image. Local magnification is highly inhomogeneous and may vary by an order of magnitude: from 0.64 to 6.7. Moreover, the anisotropy of the magnification at a point located on the facet edge may reach a factor of 10.

A simple solid-on-solid model, proposed earlier to describe overlayer-induced faceting of bcc(111) surface, is applied to faceting of spherical surfaces covered by adsorbate monolayer. Monte Carlo simulation results show that morphology of faceted surface depends on annealing temperature. At initial stage surface around the [111] pole consists of 3-sided pyramids and step-like facets, then step-like facets dominate and their number decreases with temperature, finally a single big pyramid is formed. It is shown that there is reversible phase transition at which faceted surface transforms to almost spherical one. It is found that temperature of this phase transition is an increasing function of surface curvature. Simulation results show that measurements of high temperature properties performed directly and after fast cooling to low temperature lead to different results.Comment: 8 pages, 10 figure

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