Pressure Effect on Geometric Structure of Ge R8 Phase and Its Electronic Properties

The electronic structure of Ge R8 phase has been investigated by first-principles method based on plane-wave basis, using norm-conserving pseudopotential and local density approximation. The dependence of structural parameters including lattice constants, rhombohedral angle, and atomic coordinates on pressure was also studied. The computed energy band-structure indicates that Ge R8 phase is a semimetal. Analysis of the total density of states and partial density of states shows a sharpening of valence-band edge, and the distribution of orbits was considered. At the same time, the variation of two different bond lengths was given along pressure which decreases with the increase of pressure; the underlying mechanism is also discussed.