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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ho2Hf2O7 by Materials Project

Ho2Hf2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ho3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are two shorter (2.27 Å) and six longer (2.51 Å) Ho–O bond lengths. Hf4+ is bonded to six equivalent O2- atoms to form corner-sharing HfO6 octahedra. The corner-sharing octahedral tilt angles are 53°. All Hf–O bond lengths are 2.07 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ho3+ and two equivalent Hf4+ atoms to form a mixture of distorted corner and edge-sharing OHo2Hf2 tetrahedra. In the second O2- site, O2- is bonded to four equivalent Ho3+ atoms to form OHo4 tetrahedra that share corners with sixteen OHo4 tetrahedra and edges with six equivalent OHo2Hf2 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2Hf2O5 by Materials Project

Ho2Hf2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Ho sites. In the first Ho site, Ho is bonded in a distorted body-centered cubic geometry to eight equivalent O atoms. All Ho–O bond lengths are 2.82 Å. In the second Ho site, Ho is bonded to twelve O atoms to form HoO12 cuboctahedra that share corners with four equivalent HoO12 cuboctahedra, faces with four equivalent HoO12 cuboctahedra, and faces with eight equivalent HfO5 square pyramids. There are eight shorter (2.71 Å) and four longer (2.90 Å) Ho–O bond lengths. Hf is bonded to five O atoms to form HfO5 square pyramids that share corners with five equivalent HfO5 square pyramids and faces with four equivalent HoO12 cuboctahedra. There are four shorter (2.07 Å) and one longer (2.08 Å) Hf–O bond lengths. There are two inequivalent O sites. In the first O site, O is bonded to four Ho and two equivalent Hf atoms to form a mixture of distorted edge, face, and corner-sharing OHo4Hf2 octahedra. The corner-sharing octahedra tilt angles range from 0–65°. In the second O site, O is bonded in a linear geometry to four equivalent Ho and two equivalent Hf atoms.

36 MATERIALS SCIENCE↗