Materials Data on Na5HfAs3 by Materials Project

Abstract

Na5HfAs3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are five inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a distorted see-saw-like geometry to four As3- atoms. There are a spread of Na–As bond distances ranging from 2.98–3.36 Å. In the second Na1+ site, Na1+ is bonded to five As3- atoms to form distorted NaAs5 trigonal bipyramids that share corners with two equivalent HfAs4 tetrahedra, corners with six NaAs4 tetrahedra, corners with two equivalent NaAs5 trigonal bipyramids, edges with two equivalent HfAs4 tetrahedra, edges with four NaAs4 tetrahedra, and an edgeedge with one NaAs5 trigonal bipyramid. There are a spread of Na–As bond distances ranging from 3.19–3.40 Å. In the third Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four As3- atoms. There are a spread of Na–As bond distances ranging from 3.04–3.34 Å. In the fourth Na1+ site, Na1+ is bonded to four As3- atoms to form NaAs4 tetrahedra that share corners with three equivalent HfAs4 tetrahedra, corners with five NaAs4 tetrahedra, corners with three equivalent NaAs5 trigonal bipyramids, an edgeedge with one NaAs4 tetrahedra, an edgeedge with one HfAs4 tetrahedra, and edges with two equivalent NaAs5 trigonal bipyramids. There are a spread of Na–As bond distances ranging from 2.96–2.99 Å. In the fifth Na1+ site, Na1+ is bonded to four As3- atoms to form NaAs4 tetrahedra that share corners with three equivalent NaAs4 tetrahedra, corners with five equivalent HfAs4 tetrahedra, corners with three equivalent NaAs5 trigonal bipyramids, edges with two NaAs4 tetrahedra, and edges with two equivalent NaAs5 trigonal bipyramids. There are a spread of Na–As bond distances ranging from 2.98–3.12 Å. Hf4+ is bonded to four As3- atoms to form HfAs4 tetrahedra that share corners with eight NaAs4 tetrahedra, corners with two equivalent NaAs5 trigonal bipyramids, an edgeedge with one NaAs4 tetrahedra, an edgeedge with one HfAs4 tetrahedra, and edges with two equivalent NaAs5 trigonal bipyramids. There are a spread of Hf–As bond distances ranging from 2.59–2.65 Å. There are three inequivalent As3- sites. In the first As3- site, As3- is bonded in a 1-coordinate geometry to seven Na1+ and one Hf4+ atom. In the second As3- site, As3- is bonded in a 8-coordinate geometry to six Na1+ and two equivalent Hf4+ atoms. In the third As3- site, As3- is bonded in a 9-coordinate geometry to eight Na1+ and one Hf4+ atom.