It was noted that the bonding pattern of a covalent semiconductor was disrupted when a surface was cut, while a rigid truncated bulk geometry was maintained. The covalent bonds were partially reformed (with a sizeable energy gain) when reconstruction was allowed. It was shown that the so-called electron localization function, and a first-principles pseudopotential framework, provided an invaluable insight into the bonding mechanisms. In the case of the unreconstructed surface a partly-metallic nature was detected, which disappeared upon reconstruction. In surface reformed bonds, the electron localization function sharply pictured strongly-paired electrons which were similar in character to those of the bulk bonds.

Surface Reconstructions and Bonding via the Electron Localization Function - the Case of Si(001) L.De Santis, R.Resta: Solid State Communications, 1999, 111[10], 583-8