Structural, electronic and optical properties of some polymorphs of germanium and amorphous germanium

Ge 3 and Ge 4 are two high pressure crystal phases of germanium which have some of the structural features believed to be present in amorphous germanium. The atomic arrangements and electronic and optical properties of Ge 3 and Ge 4 are calculated. The properties of Ge 3 are found to show many similarities to those of amorphous germanium.