Further findings of X-ray absorption near-edge structure in lithium manganese spinel oxide using first-principles calculations

X-ray absorption near-edge structure (XANES) spectroscopy, which reveals the features of the electronic and local structure, of lithium manganese oxides LixMn2O4 (x = 0-2) was examined using first-principles calculations. Both the easily observable parts and the tiny peaks of the theoretical Mn K-edge XANES spectra agreed with the experimental spectra. From the theoretical results of two anti-ferromagnetic LiMn2O4 models, the contributions of the Mn3+ ion and Mn4+ ion centers to the XANES spectra differ due to the difference in the overlap between the Mn 4p partial density of state (PDOS) and the O 2p PDOS. Similar results can be also seen by comparing the theoretical XANES spectra and the PDOS between Li(Mn3+ Mn4+)O-4 and de-intercalated Li(0.)5(Mn0.53+Mn1.54+)O-4 and Mn24+O4 (lambda-MnO2). The XANES spectral changes with the lithium ion displacement (six-to four-coordination) due to the phase transition (cubic Fd (3) over barm LiMn2O4 to tetragonal I4(1)/amd Li2Mn2O4) can be determined by the indirect contribution of the Li 2p PDOS to the Mn 4p PDOS via the O 2p PDOS.