Materials Data on NaCr5Se8 by Materials Project
NaCr5Se8 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na1+ is bonded in a 10-coordinate geometry to ten Se2- atoms. There are a spread of Na–Se bond distances ranging from 3.46–3.71 Å. There are three inequivalent Cr3+ sites. In the first Cr3+ site, Cr3+ 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 four shorter (2.52 Å) and two longer (2.54 Å) Cr–Se bond lengths. In the second Cr3+ site, Cr3+ 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 49–51°. There are a spread of Cr–Se bond distances ranging from 2.50–2.66 Å. In the third Cr3+ site, Cr3+ 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 49–51°. There are a spread of Cr–Se bond distances ranging from 2.50–2.64 Å. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to one Na1+ and four Cr3+ atoms. In the second Se2- site, Se2- is bonded in a 5-coordinate geometry to two equivalent Na1+ and three Cr3+ atoms. In the third Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Na1+ and three equivalent Cr3+ atoms. In the fourth Se2- site, Se2- is bonded to five Cr3+ atoms to form distorted edge-sharing SeCr5 trigonal bipyramids.