Valence electron distribution in La2 Li½ Cu½ O4, Nd2 Li½ Ni½ O4, and La2 Li½ Co½ O4

Abstract

The distribution of valence electrons between transition metals (TM) and oxygen has been studied via X-ray absorption near-edge fine structure (XANES) at the TM-L2,3 and O-K thresholds for La2 Li½ Cu½ O4 , Nd2 Li½ Ni½ O4 , and La2 Li½ Co½ O4 . Simulations of the TM-L2,3 XANES by charge-transfer multiplet calculations result in 3d-hole concentrations that increase from ~30% 3d^8 in the Cu(III) to ~57% 3d^7 in the Ni(III) to ~72% 3d^6 in the Co(III) compound. Concomitantly, the O-K XANES spectra reflect an increase of bond ionicity in the same sequence. The results show that the Li-doped holes in Nd2 Li½ Ni½ O4 are distributed between Ni-3d and O-2p orbitals.