DOI: 10.17188/1282910
title: Materials Data on Na3Cr11Se20 by Materials Project

description: Na3Cr11Se20 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.85–3.04 Å. In the second Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 pentagonal pyramids that share corners with seven CrSe6 octahedra, edges with three CrSe6 octahedra, and edges with two equivalent NaSe6 pentagonal pyramids. The corner-sharing octahedra tilt angles range from 9–49°. There are a spread of Na–Se bond distances ranging from 3.00–3.12 Å. In the third Na1+ site, Na1+ is bonded in a 6-coordinate geometry to six Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.98–3.11 Å. There are eleven inequivalent Cr+3.36+ sites. In the first Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are five shorter (2.53 Å) and one longer (2.58 Å) Cr–Se bond lengths. In the second Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form a mixture of edge and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Cr–Se bond distances ranging from 2.45–2.63 Å. In the third Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Cr–Se bond distances ranging from 2.45–2.71 Å. In the fourth Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°. There are a spread of Cr–Se bond distances ranging from 2.54–2.57 Å. In the fifth Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. There are a spread of Cr–Se bond distances ranging from 2.44–2.67 Å. In the sixth Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with four CrSe6 octahedra, a cornercorner with one NaSe6 pentagonal pyramid, and edges with six CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 48–50°. There are a spread of Cr–Se bond distances ranging from 2.53–2.58 Å. In the seventh Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with four CrSe6 octahedra, corners with two equivalent NaSe6 pentagonal pyramids, and edges with four CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 50–53°. There are a spread of Cr–Se bond distances ranging from 2.50–2.62 Å. In the eighth Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with two equivalent CrSe6 octahedra, edges with six CrSe6 octahedra, edges with two equivalent NaSe6 pentagonal pyramids, and a faceface with one CrSe6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are a spread of Cr–Se bond distances ranging from 2.51–2.61 Å. In the ninth Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedra tilt angles range from 47–55°. There are a spread of Cr–Se bond distances ranging from 2.44–2.69 Å. In the tenth Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with two equivalent CrSe6 octahedra, corners with two equivalent NaSe6 pentagonal pyramids, edges with six CrSe6 octahedra, and an edgeedge with one NaSe6 pentagonal pyramid. The corner-sharing octahedral tilt angles are 49°. There are a spread of Cr–Se bond distances ranging from 2.48–2.63 Å. In the eleventh Cr+3.36+ site, Cr+3.36+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with two equivalent CrSe6 octahedra, corners with two equivalent NaSe6 pentagonal pyramids, and edges with four CrSe6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Cr–Se bond distances ranging from 2.38–2.56 Å. There are twenty inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Na1+ and three Cr+3.36+ atoms to form SeNa2Cr3 square pyramids that share corners with three SeCr5 trigonal bipyramids, edges with two equivalent SeNa3Cr3 octahedra, edges with two equivalent SeNa2Cr3 square pyramids, and an edgeedge with one SeNa2Cr3 trigonal bipyramid. In the second Se2- site, Se2- is bonded in a 3-coordinate geometry to three Cr+3.36+ atoms. In the third Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Cr+3.36+ atoms. In the fourth Se2- site, Se2- is bonded to five Cr+3.36+ atoms to form distorted SeCr5 square pyramids that share a cornercorner with one SeNa2Cr3 trigonal bipyramid, corners with two equivalent SeNaCr3 trigonal pyramids, edges with two equivalent SeCr5 square pyramids, and an edgeedge with one SeNaCr3 trigonal pyramid. In the fifth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to one Na1+ and three Cr+3.36+ atoms. In the sixth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Cr+3.36+ atoms. In the seventh Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Cr+3.36+ atoms. In the eighth Se2- site, Se2- is bonded in a distorted T-shaped geometry to three Cr+3.36+ atoms. In the ninth Se2- site, Se2- is bonded to three Na1+ and three Cr+3.36+ atoms to form SeNa3Cr3 octahedra that share corners with two equivalent SeCr5 trigonal bipyramids, corners with two equivalent SeNaCr3 trigonal pyramids, edges with four SeNa3Cr3 octahedra, and an edgeedge with one SeCr5 trigonal bipyramid. In the tenth Se2- site, Se2- is bonded in a 5-coordinate geometry to five Cr+3.36+ atoms. In the eleventh Se2- site, Se2- is bonded in a distorted trigonal planar geometry to three Cr+3.36+ atoms. In the twelfth Se2- site, Se2- is bonded to one Na1+ and three Cr+3.36+ atoms to form SeNaCr3 trigonal pyramids that share corners with two equivalent SeNa3Cr3 octahedra, corners with two equivalent SeCr5 square pyramids, corners with two equivalent SeNaCr3 trigonal pyramids, and an edgeedge with one SeCr5 square pyramid. The corner-sharing octahedral tilt angles are 40°. In the thirteenth Se2- site, Se2- is bonded to three Na1+ and three Cr+3.36+ atoms to form distorted SeNa3Cr3 octahedra that share corners with two equivalent SeNa2Cr3 trigonal bipyramids, edges with four SeNa3Cr3 octahedra, edges with two equivalent SeNa2Cr3 square pyramids, and edges with two equivalent SeCr5 trigonal bipyramids. In the fourteenth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to four Cr+3.36+ atoms. In the fifteenth Se2- site, Se2- is bonded in a distorted trigonal planar geometry to three Cr+3.36+ atoms. In the sixteenth Se2- site, Se2- is bonded in a 5-coordinate geometry to three Na1+ and two equivalent Cr+3.36+ atoms. In the seventeenth Se2- site, Se2- is bonded to five Cr+3.36+ atoms to form distorted SeCr5 trigonal bipyramids that share corners with two equivalent SeNa3Cr3 octahedra, a cornercorner with one SeNa2Cr3 square pyramid, edges with three SeNa3Cr3 octahedra, and edges with two equivalent SeCr5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 3°. In the eighteenth Se2- site, Se2- is bonded in a 4-coordinate geometry to three Na1+ and one Cr+3.36+ atom. In the nineteenth Se2- site, Se2- is bonded in a 3-coordinate geometry to three Cr+3.36+ atoms. In the twentieth Se2- site, Se2- is bonded to two equivalent Na1+ and three Cr+3.36+ atoms to form distorted SeNa2Cr3 trigonal bipyramids that share corners with two equivalent SeNa3Cr3 octahedra, corners with three SeNa2Cr3 square pyramids, an edgeedge with one SeNa2Cr3 square pyramid, and edges with two equivalent SeNa2Cr3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 43°.