Electronic Band Structure of Th₃Ni₃Sb₄and Th₃X₄(X=P, As, Sb)

Abstract

In order to clarify the origin of the semiconductor like behavior of U 3 Ni 3 Sb 4 , one-electron energy band structures for the isostructural Th 3 Ni 3 Sb 4 and the Th 3 P 4 type Th 3 X 4 (X=P, As, Sb), which belong to the same space group, are calculated by the self-consistent APW method with the local density approximation. The calculated results for Th 3 X 4 show that the compounds are the narrow gap semiconductor or semimetal; the valence bands are derived from the X p states and the conduction bands from the Th 6 d states. Th 3 Ni 3 Sb 4 is also the semiconductor and the valence bands consist of the Ni 3 d and Sb 5 p states. Due to the mixing between the Ni 3 d and Th 6 d states, the empty Th 6 d conduction band is shifted up resulting a gap of 0.36 eV. This result explains reasonably why U 3 X 4 is semimetal but U 3 Ni 3 Sb 4 is semiconductor with a gap of 0.2 eV.