DOI: 10.17188/1267722
title: Materials Data on Na8Nb2Cu4S21 by Materials Project

description: Na8Nb2Cu4S21 crystallizes in the orthorhombic P2_12_12 space group. The structure is three-dimensional. there are five inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six S+1.24- atoms. There are a spread of Na–S bond distances ranging from 2.82–3.14 Å. In the second Na1+ site, Na1+ is bonded to five S+1.24- atoms to form NaS5 trigonal bipyramids that share a cornercorner with one NaS7 pentagonal bipyramid, a cornercorner with one NaS6 pentagonal pyramid, a cornercorner with one NbS4 tetrahedra, corners with three CuS4 tetrahedra, edges with two equivalent NaS6 octahedra, an edgeedge with one NbS4 tetrahedra, and an edgeedge with one CuS4 tetrahedra. There are a spread of Na–S bond distances ranging from 2.84–3.06 Å. In the third Na1+ site, Na1+ is bonded to six S+1.24- atoms to form distorted NaS6 octahedra that share a cornercorner with one NaS7 pentagonal bipyramid, a cornercorner with one NaS6 pentagonal pyramid, a cornercorner with one NbS4 tetrahedra, corners with three CuS4 tetrahedra, an edgeedge with one NbS4 tetrahedra, an edgeedge with one CuS4 tetrahedra, and edges with two equivalent NaS5 trigonal bipyramids. There are a spread of Na–S bond distances ranging from 2.84–3.22 Å. In the fourth Na1+ site, Na1+ is bonded to six S+1.24- atoms to form distorted NaS6 pentagonal pyramids that share corners with two equivalent NaS6 octahedra, corners with two equivalent NaS7 pentagonal bipyramids, corners with eight CuS4 tetrahedra, corners with two equivalent NaS5 trigonal bipyramids, edges with two equivalent NaS7 pentagonal bipyramids, and edges with two equivalent NbS4 tetrahedra. The corner-sharing octahedral tilt angles are 74°. There are a spread of Na–S bond distances ranging from 3.05–3.13 Å. In the fifth Na1+ site, Na1+ is bonded to seven S+1.24- atoms to form distorted NaS7 pentagonal bipyramids that share corners with two equivalent NaS6 octahedra, corners with two equivalent NaS6 pentagonal pyramids, corners with four equivalent NbS4 tetrahedra, corners with two equivalent NaS5 trigonal bipyramids, edges with two equivalent NaS6 pentagonal pyramids, and edges with four CuS4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of Na–S bond distances ranging from 3.00–3.12 Å. Nb5+ is bonded to four S+1.24- atoms to form NbS4 tetrahedra that share a cornercorner with one NaS6 octahedra, corners with two equivalent NaS7 pentagonal bipyramids, a cornercorner with one NaS5 trigonal bipyramid, an edgeedge with one NaS6 octahedra, an edgeedge with one NaS6 pentagonal pyramid, edges with two CuS4 tetrahedra, and an edgeedge with one NaS5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 52°. There are a spread of Nb–S bond distances ranging from 2.30–2.33 Å. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded to four S+1.24- atoms to form CuS4 tetrahedra that share corners with two equivalent NaS6 octahedra, corners with two equivalent NaS6 pentagonal pyramids, corners with three equivalent CuS4 tetrahedra, a cornercorner with one NaS5 trigonal bipyramid, an edgeedge with one NaS7 pentagonal bipyramid, an edgeedge with one NbS4 tetrahedra, and an edgeedge with one NaS5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 21–25°. There are a spread of Cu–S bond distances ranging from 2.30–2.36 Å. In the second Cu2+ site, Cu2+ is bonded to four S+1.24- atoms to form CuS4 tetrahedra that share a cornercorner with one NaS6 octahedra, corners with two equivalent NaS6 pentagonal pyramids, corners with three equivalent CuS4 tetrahedra, corners with two equivalent NaS5 trigonal bipyramids, an edgeedge with one NaS6 octahedra, an edgeedge with one NaS7 pentagonal bipyramid, and an edgeedge with one NbS4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. There are a spread of Cu–S bond distances ranging from 2.29–2.40 Å. There are eleven inequivalent S+1.24- sites. In the first S+1.24- site, S+1.24- is bonded in a 3-coordinate geometry to one Na1+ and two S+1.24- atoms. There are one shorter (2.07 Å) and one longer (2.10 Å) S–S bond lengths. In the second S+1.24- site, S+1.24- is bonded in a 5-coordinate geometry to two Na1+, one Nb5+, and two Cu2+ atoms. In the third S+1.24- site, S+1.24- is bonded in a 5-coordinate geometry to three Na1+, one Nb5+, and one Cu2+ atom. In the fourth S+1.24- site, S+1.24- is bonded in a 5-coordinate geometry to two Na1+, two Cu2+, and one S+1.24- atom. In the fifth S+1.24- site, S+1.24- is bonded in a 5-coordinate geometry to three Na1+, one Nb5+, and one Cu2+ atom. In the sixth S+1.24- site, S+1.24- is bonded in a 5-coordinate geometry to four Na1+ and one S+1.24- atom. The S–S bond length is 2.08 Å. In the seventh S+1.24- site, S+1.24- is bonded in a distorted trigonal planar geometry to one Na1+ and two equivalent S+1.24- atoms. Both S–S bond lengths are 2.09 Å. In the eighth S+1.24- site, S+1.24- is bonded to four Na1+ and one Nb5+ atom to form distorted corner-sharing SNa4Nb trigonal bipyramids. In the ninth S+1.24- site, S+1.24- is bonded in a 4-coordinate geometry to two Na1+ and two S+1.24- atoms. The S–S bond length is 2.07 Å. In the tenth S+1.24- site, S+1.24- is bonded in a distorted water-like geometry to two S+1.24- atoms. In the eleventh S+1.24- site, S+1.24- is bonded in a 5-coordinate geometry to two Na1+, two Cu2+, and one S+1.24- atom.