Materials Data on Na3(FeSe2)2 by Materials Project
Na3(FeSe2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with eight equivalent FeSe4 tetrahedra, edges with two equivalent FeSe4 tetrahedra, and faces with two equivalent NaSe6 octahedra. There are a spread of Na–Se bond distances ranging from 2.94–3.11 Å. In the second 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 2.95–3.56 Å. Fe+2.50+ is bonded to four Se2- atoms to form FeSe4 tetrahedra that share corners with four equivalent NaSe6 octahedra, an edgeedge with one NaSe6 octahedra, and edges with two equivalent FeSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 14–63°. There are a spread of Fe–Se bond distances ranging from 2.39–2.42 Å. There are three inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 6-coordinate geometry to four Na1+ and two equivalent Fe+2.50+ atoms. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to four equivalent Na1+ and two equivalent Fe+2.50+ atoms. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to five Na1+ and two equivalent Fe+2.50+ atoms.