Materials Data on Na2(CrSe2)3 by Materials Project
Na2(CrSe2)3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na1+ is bonded to six Se2- atoms to form distorted NaSe6 octahedra that share corners with six CrSe6 octahedra, edges with three equivalent NaSe6 octahedra, and edges with six CrSe6 octahedra. The corner-sharing octahedral tilt angles are 12°. All Na–Se bond lengths are 3.01 Å. There are two inequivalent Cr+3.33+ sites. In the first Cr+3.33+ site, Cr+3.33+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with four equivalent NaSe6 octahedra, edges with four equivalent NaSe6 octahedra, and edges with six equivalent CrSe6 octahedra. The corner-sharing octahedral tilt angles are 12°. There are four shorter (2.54 Å) and two longer (2.55 Å) Cr–Se bond lengths. In the second Cr+3.33+ site, Cr+3.33+ is bonded to six Se2- atoms to form CrSe6 octahedra that share corners with four equivalent NaSe6 octahedra, edges with four equivalent NaSe6 octahedra, and edges with six CrSe6 octahedra. The corner-sharing octahedral tilt angles are 12°. All Cr–Se bond lengths are 2.54 Å. There are two inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to two equivalent Na1+ and three Cr+3.33+ atoms to form a mixture of edge and corner-sharing SeNa2Cr3 square pyramids. In the second Se2- site, Se2- is bonded to two equivalent Na1+ and three Cr+3.33+ atoms to form a mixture of edge and corner-sharing SeNa2Cr3 square pyramids.