Electronic structural change due to crystal structural transformation from γ- to β-phases of Li7VN4

Abstract

The difference in electronic structure between the β-phase (space group: Pa-3) and the γ-phase (P-43n) of Li7VN4 is studied. Li7VN4 crystallizes in the γ-phase with all the VN4 tetrahedral clusters isolated or the β-phase with all the VN4 formed into the isolated pairs of two neighbor VN4 clusters jointed at their corners, depending on the distribution of V atoms in a zinc blende GaN-like Li7VN4 framework. γ- and β-Li7VN4 have similar optical band gaps (1.13eV and 1.10eV, respectively). β-Li7VN4 shows a metallic electron configuration due to the partially occupied V-3d related valence band as a result of the V-3d orbital spreading into the neighbor VN4 clusters, while γ-Li7VN4 possesses a semiconducting configuration with the band gap between the completely occupied N-2p valence band and the V-3d related conduction band. γ-Li7VN4 shows a much higher electric resistivity (∼108Ωcm) than that of β-Li7VN4 (∼104Ωcm), which reflect the difference in the electronic structure between γ- and β-Li7VN4.