First-principles LDA+U and GGA+U study of cerium oxides: Dependence on the effective U parameter

The electronic structure and properties of cerium oxides CeO2 and Ce2O3 have been studied in the framework of the LDA+U and GGAPW91+U implementations of density functional theory. The depen-dence of selected observables of these materials on the effective U parameter has been investigated in detail. The examined properties include lattice constants, bulk moduli, density of states, and formation energies of CeO2 and Ce2O3. For CeO2, the LDA+U results are in better agreement with experiment than the GGA+U results whereas for the computationally more demanding Ce2O3 both approaches give comparable accuracy. Furthermore, as expected, Ce2O3 is much more sensitive to the choice of the U value. Generally, the PW91 functional provides an optimal agreement with experiment at lower U energies than LDA does. In order to achieve a balanced description of both kinds of materials, and also of nonstoichiometric CeO2−x phases, an appropriate choice of U is suggested for LDA+U and GGA+U schemes. Nevertheless, an optimum value appears to be property dependent, especially for Ce2O3. Optimum U values are found to be, in general, larger than values determined previously in a self-consistent way. DOI: 10.1103/PhysRevB.75.035115 PACS numbers: 71.15.Mb, 71.28.d, 71.30.h I