The possibilities of graphic STM image simulation of a clean Si(1 1 1) 7 x 7 surface at atomic level are indicated. The presented procedure takes into account various types of deformation on the surface near the Fermi level in order to classify them and explain their origin. It also gives a clear hint to insert relevant physical phenomena in a suggested analysis. This goal is achieved exploiting the results of DAS (dimmer adatom stacing fault) model by means of standard mathematical programmes. A clean Si(1 1 1) 7 x 7 surface is considered as the representative example, but similar evaluation is possible for another non-metal and metal surfaces. (c) 2006 Elsevier B.V. All fights reserved.