Valence electron distribution in La2Li1/2Cu1/2O4, Nd2Li1/2Ni1/2O4, and La2Li1/2Co1/2O4

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 La2Li1/2Cu1/2O4, Nd2Li1/2Ni1/2O4, and La2Li1/2Co1/2O4. Simulations of the TM-L2, 3 XANES by charge-transfer multiplet calculations result in 3d-hole concentrations that increase from ∼30% 3d8 in the Cu(III) to ∼57% 3d7 in the Ni(III) to ∼72% 3d6 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 Nd2Li1/2Ni1/2O4 are distributed between Ni-3d and O-2p orbitals.