Electronic structural difference between Li7VN4 and Li7MnN4 due to the replacement of V with Mn: A simulation by a discrete variational Xa method

摘要

The difference in electronic structure of Li_7MN_4 (M=V and Mn) due to the replacement of V with Mn is studied by the discrete variational (DV) Xa method. Li_7VN_4 and Li_7MnN_4 crystallize in the same zincblende- like structure (space group: P-43n) with similar lattice constants of 9.6090 and 9.5548 A , respectively. The DV-Xa calculations show that Li_7VN_4 is a semiconductor with energy gap between the empty V-3d related band and the completely occupied N-2p band, while Li7MnN4 has a metallic electron configuration because of the partially occupied Mn-3d related band located above the completely filled N-2p band, exhibiting the shift of the Fermi level caused by an increase in electron due to the replacement of V with Mn, where Mn (electron configuration: 3d~54s~2) owns two more 3d electrons than V (3d~34s~2) does. Electron paramagnetic resonance and magnetic susceptibility measurements reveal that Li7MnN4 is paramagnetic, resulting from the electrons partially occupying the Mn-3d related band, while Li7VN_4 is diamagnetic, arising from the un-occupation of the V-3d related band. These experiments support the computational results.