Experimental scanning tunnelling microscopy data for the Si(111)5 x 5
- 2 x 1 phase boundary are analysed with reference to the structure of
the 2 x 1 surface. The height change data are subject to significant
correction factors, making interpretation difficult due to the small t
heoretical differences involved. The theoretical lateral differences a
re much larger, being 3.3 angstrom, and these are analysed.