Unified description of silicon (111) surface transitions

It is assumed that a strained strip of about 25 {} width occurs at the bases of steps on Si(111) surfaces. Evidence supporting this is summarized and quantitative estimates for the strain energy and strain at the edge of the strip yield approximately 0.32 eV and 0.1, respectively, which are sufficient to inhibit reconstruction. The various structural transitions that occur on Si(111) are then accounted for in a natural and unified way.