Electronic structure of rare-earth sesquioxides and oxysulfides

Rare-earth sesquioxides R2O3 and oxysulfides R2O2S (R = La, Cc, and Pr) have been theoretically investigated by first-principles pseudopotentiat method based on local density approximation in density functional theory. The structural, electronic, vibrational and dielectric properties of the rare-earth compounds are investigated with rare-earth psuedopotentials with 4f-electrons of rare-earth atoms as core states. Calculated properties related to the ground states appear consistent with the experimental results. The calculation result also indicates a possibility of another phonon mode assignment from Raman spectra of La2O3. The present work also implies that 4f-states are essential in electronic excitations to explain the variation of photo-absorption and body-color of R2O3/R2O2S. (c) 2005 Elsevier B.V. All rights reserved.