Materials Data on Na5Hf2F13 by Materials Project

Abstract

Na5Hf2F13 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a body-centered cubic geometry to eight F1- atoms. There are a spread of Na–F bond distances ranging from 2.41–2.52 Å. In the second Na1+ site, Na1+ is bonded in a body-centered cubic geometry to eight F1- atoms. There are four shorter (2.32 Å) and four longer (2.60 Å) Na–F bond lengths. In the third Na1+ site, Na1+ is bonded to six F1- atoms to form distorted NaF6 pentagonal pyramids that share corners with four equivalent HfF7 pentagonal bipyramids, an edgeedge with one HfF7 pentagonal bipyramid, and edges with two equivalent NaF6 pentagonal pyramids. There are four shorter (2.33 Å) and two longer (2.40 Å) Na–F bond lengths. Hf4+ is bonded to seven F1- atoms to form distorted HfF7 pentagonal bipyramids that share a cornercorner with one HfF7 pentagonal bipyramid, corners with four equivalent NaF6 pentagonal pyramids, and an edgeedge with one NaF6 pentagonal pyramid. There are a spread of Hf–F bond distances ranging from 2.05–2.14 Å. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded to three Na1+ and one Hf4+ atom to form a mixture of distorted edge and corner-sharing FNa3Hf tetrahedra. In the second F1- site, F1- is bonded to three Na1+ and one Hf4+ atom to form a mixture of edge and corner-sharing FNa3Hf tetrahedra. In the third F1- site, F1- is bonded in a 4-coordinate geometry to three Na1+ and one Hf4+ atom. In the fourth F1- site, F1- is bonded in a linear geometry to two equivalent Hf4+ atoms.