DOE OSTI2020
Na7In3Se8 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are seven inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 octahedra that share corners with seven NaSe6 octahedra, a cornercorner with one NaSe4 tetrahedra, corners with five InSe4 tetrahedra, edges with six NaSe6 octahedra, edges with three InSe4 tetrahedra, and a faceface with one NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 18–52°. There are a spread of Na–Se bond distances ranging from 2.88–3.54 Å. In the second Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 octahedra that share corners with seven NaSe6 octahedra, corners with two equivalent NaSe4 tetrahedra, corners with four InSe4 tetrahedra, edges with six NaSe6 octahedra, edges with three InSe4 tetrahedra, and a faceface with one NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 15–53°. There are a spread of Na–Se bond distances ranging from 2.88–3.65 Å. In the third Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 octahedra that share corners with seven NaSe6 octahedra, corners with two equivalent NaSe4 tetrahedra, corners with four InSe4 tetrahedra, edges with six NaSe6 octahedra, an edgeedge with one NaSe4 tetrahedra, edges with two InSe4 tetrahedra, and a faceface with one NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 11–60°. There are a spread of Na–Se bond distances ranging from 2.93–3.61 Å. In the fourth Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with seven NaSe6 octahedra, a cornercorner with one NaSe4 tetrahedra, corners with five InSe4 tetrahedra, edges with six NaSe6 octahedra, an edgeedge with one InSe4 tetrahedra, edges with two equivalent NaSe4 tetrahedra, and a faceface with one NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 10–60°. There are a spread of Na–Se bond distances ranging from 2.96–3.49 Å. In the fifth Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with ten NaSe6 octahedra, a cornercorner with one NaSe4 tetrahedra, corners with three InSe4 tetrahedra, edges with two NaSe6 octahedra, an edgeedge with one NaSe4 tetrahedra, edges with three InSe4 tetrahedra, and faces with two NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 36–60°. There are a spread of Na–Se bond distances ranging from 2.89–3.27 Å. In the sixth Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with ten NaSe6 octahedra, a cornercorner with one NaSe4 tetrahedra, corners with three InSe4 tetrahedra, edges with two NaSe6 octahedra, an edgeedge with one NaSe4 tetrahedra, edges with three InSe4 tetrahedra, and faces with two NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 34–60°. There are a spread of Na–Se bond distances ranging from 2.90–3.38 Å. In the seventh Na1+ site, Na1+ is bonded to four Se2- atoms to form NaSe4 tetrahedra that share corners with eight NaSe6 octahedra, corners with two InSe4 tetrahedra, edges with five NaSe6 octahedra, and an edgeedge with one InSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–77°. There are a spread of Na–Se bond distances ranging from 2.89–2.94 Å. There are three inequivalent In3+ sites. In the first In3+ site, In3+ is bonded to four Se2- atoms to form InSe4 tetrahedra that share corners with eight NaSe6 octahedra, corners with two InSe4 tetrahedra, edges with five NaSe6 octahedra, and an edgeedge with one NaSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–66°. There are a spread of In–Se bond distances ranging from 2.56–2.70 Å. In the second In3+ site, In3+ is bonded to four Se2- atoms to form InSe4 tetrahedra that share corners with eight NaSe6 octahedra, a cornercorner with one NaSe4 tetrahedra, a cornercorner with one InSe4 tetrahedra, edges with five NaSe6 octahedra, and an edgeedge with one InSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 21–68°. There are a spread of In–Se bond distances ranging from 2.58–2.68 Å. In the third In3+ site, In3+ is bonded to four Se2- atoms to form InSe4 tetrahedra that share corners with eight NaSe6 octahedra, a cornercorner with one NaSe4 tetrahedra, a cornercorner with one InSe4 tetrahedra, edges with five NaSe6 octahedra, and an edgeedge with one InSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–69°. There are a spread of In–Se bond distances ranging from 2.58–2.68 Å. There are eight inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to four Na1+ and two equivalent In3+ atoms to form distorted SeNa4In2 pentagonal pyramids that share a cornercorner with one SeNa5In pentagonal pyramid and edges with three SeNa4In2 pentagonal pyramids. In the second Se2- site, Se2- is bonded in a 7-coordinate geometry to six Na1+ and one In3+ atom. In the third Se2- site, Se2- is bonded in a 7-coordinate geometry to five Na1+ and two In3+ atoms. In the fourth Se2- site, Se2- is bonded in a 7-coordinate geometry to five Na1+ and two In3+ atoms. In the fifth Se2- site, Se2- is bonded in a 7-coordinate geometry to six Na1+ and one In3+ atom. In the sixth Se2- site, Se2- is bonded in a 6-coordinate geometry to five Na1+ and one In3+ atom. In the seventh Se2- site, Se2- is bonded to four Na1+ and two equivalent In3+ atoms to form distorted SeNa4In2 pentagonal pyramids that share a cornercorner with one SeNa5In pentagonal pyramid and edges with three SeNa4In2 pentagonal pyramids. In the eighth Se2- site, Se2- is bonded to five Na1+ and one In3+ atom to form a mixture of distorted edge and corner-sharing SeNa5In pentagonal pyramids.