First-principles study of structural and energetic properties of A₂Hf₂O₇ (A=Dy, Ho, Er) compounds

The structural and energetic properties of A₂Hf₂O₇ (A=Dy, Ho, Er) compounds have been investigated by means of ab initio total energy calculations. For Er₂Hf₂O₇ the defect fluorite structure is predicted to be more stable than pyrochlore structure, agreeing well with previous experimental [J. Inorg. Nucl. Chem. 31, 2367 (1969); J. Less Common Met. 14, 435 (1968)] and theoretical [J. Am. Ceram. Soc. 85, 2139 (2002)] investigations. In contrast to Er₂Hf₂O₇ pyrochlore, Dy₂Hf₂O₇ and Ho₂Hf₂O₇ prefer pyrochlore structures, which is consistent with the recent experimental observations of Dy₂Hf₂O₇ compound [J. Solid State Chem. 179, 1990 (2006)].