A study was made, of the effect of surface defects upon the structure of a (001) surface, by means of statistical mechanical calculations which were based upon an asymmetrical dimer model. The local effect of surface defects had been identified by means of scanning tunnelling microscopy. The arrangement of dimer images near to the defect was well reproduced, at both low and high temperatures, by the calculated scanning tunnelling microscope images. It was found that, for a certain configuration involving a few defects, the effect of the defects was much greater than a simple sum of isolated defects at low temperatures. This indicated why a wide region of apparently symmetrical images was observed, in an area with a rather low defect density, in a low-temperature scanning tunnelling microscope image.

Y.Nakamura, H.Kawai, M.Nakayama: Physical Review B, 1995, 52[11], 8231-8