Materials Data on Na2Hf2O5 by Materials Project
Na2Hf2O5 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Na–O bond lengths are 2.57 Å. In the second Na1+ site, Na1+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All Na–O bond lengths are 2.82 Å. Hf4+ is bonded to five O2- atoms to form distorted corner-sharing HfO5 square pyramids. There are one shorter (1.99 Å) and four longer (2.04 Å) Hf–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Hf4+ atoms. In the second O2- site, O2- is bonded to four equivalent Na1+ and two equivalent Hf4+ atoms to form a mixture of distorted edge and corner-sharing ONa4Hf2 octahedra. The corner-sharing octahedral tilt angles are 0°.