Stability and Half-metallicity of Transition Metal Pnictides in Tetrahedrally Bonded Structures

Using a full potential linearized muffin-tin approach and the spin polarized density functional method, we studied the magnetism and the electronic structure for transition metal pnictides in the zinc blende (ZB) and the wurtzite (WZ) structures under volume expansion and compression. It was found that for many compounds the WZ structure has lower total energy than the ZB structure. The energy difference between the two tetrahedrally bonded structures are only a few meV, which indicates that the system may form other polytypes with stacking intermediate between ZB and WZ. Both ZB and WZ structure are half-metallic. There are only slight differences between ZB and WZ structures in the resulting band gaps of the minority spin and the density of states (DOS) at the Fermi level for the majority spin. This indicates that these properties are only determined by the local bonding. The minority gap and the DOS at the Fermi level are found to be strongly dependent on the volume expansion.