Character tables for the "group of the wave vector" at certain points of symmetry in the Brillouin zone are given. The additional degeneracies due to time reversal symmetry are indicated. The form of energy vz wave vector at these points of symmetry is derived. A possible reason for the complications which may make a simple effective mass concept invalid for some crystals of this type structure will be presented. HE e6'ect of symmetry on the energy band structures of crystals of the zinc blende type can be readily derived using the machinery developed by Bouck.aert, Smoluchowski, and Wigner' and Elliott. '
Recent extensive studies of the semiconductor proper- ties' of InSb, which has the zinc blende structure, and preliminary cyclotron resonance investigations' have indicated a need for a more thorough understanding of the possible energy band structures of a zinc blende type crystal.
A zinc blende structure consists of two interpene- trating face centered cubic lattices; each f.c.c. may be considered a sublattice. The two sublattices are dis- placed by one quarter of a body diagonal and each consists entirely of one species of atom. If the two sub- lattices are identical, one has a diamond structure. The symmetry properties of diamond are fully discussed in reference 2.
FxG. 1. The erst Brillouin zone for a face centered cubic, diamond, and zinc blende structure. Points and lines of symmetry are indicated using the notation of reference 1.