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Density functional theory study of La 2 Ce 2 O 7 : Disordered fluorite versus pyrochlore structure

2011; American Physical Society; Volume: 84; Issue: 5 Linguagem: Inglês

10.1103/physrevb.84.054110

1550-235X

Danny E. P. Vanpoucke, Patrick Bultinck, Stefaan Cottenier, Véronique Van Speybroeck, Isabel Van Driessche,

Nuclear Materials and Properties

The crystal structure of lanthanum cerium oxide (La${}_{2}$Ce${}_{2}$O${}_{7}$) is investigated using ab initio density functional theory calculations. The relative stability of fluorite- and pyrochlorelike structures is studied through comparison of their formation energies. These formation energies show the pyrochlore structure to be favored over the fluorite structure, apparently contradicting the conclusions based on experimental neutron and x-ray diffraction (XRD). By calculating and comparing XRD spectra for a set of differently ordered and random structures, we show that the pyrochlore structure is consistent with diffraction experiments. For these reasons, we suggest the pyrochlore structure as the ground-state crystal structure for La${}_{2}$Ce${}_{2}$O${}_{7}$.