Pseudopotential calculation of the surface band structure of Si(111) faces

The surface Green-function method is used to calculate the surface band structure of Si(111) faces as described by the conventional abrupt step model. The calculation yields a single narrow band located in the absolute thermal gap, in qualitative agreement with previous tight-binding calculations for this face, but differing from experimental data. An approximation suggested by the above method consists in neglecting the plane waves with wavevector lying outside the Jones zone. This approximation is studied analytically, including a careful description of the wavefunctions near the surface.