Materials Data on Na5AgGe2Se7 by Materials Project

Abstract

Na5AgGe2Se7 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six Se2- atoms to form NaSe6 octahedra that share corners with two equivalent NaSe6 octahedra, corners with two equivalent GeSe4 tetrahedra, edges with four equivalent NaSe6 octahedra, edges with two equivalent AgSe4 tetrahedra, and edges with two equivalent GeSe4 tetrahedra. The corner-sharing octahedral tilt angles are 9°. There are a spread of Na–Se bond distances ranging from 3.02–3.24 Å. In the second Na1+ site, Na1+ is bonded to six Se2- atoms to form distorted NaSe6 octahedra that share corners with two NaSe6 octahedra, a cornercorner with one GeSe4 tetrahedra, corners with three equivalent AgSe4 tetrahedra, edges with four NaSe6 octahedra, and edges with three equivalent GeSe4 tetrahedra. The corner-sharing octahedra tilt angles range from 9–37°. There are a spread of Na–Se bond distances ranging from 3.07–3.20 Å. In the third Na1+ site, Na1+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Na–Se bond distances ranging from 2.92–3.17 Å. Ag1+ is bonded to four Se2- atoms to form distorted AgSe4 tetrahedra that share corners with six equivalent NaSe6 octahedra, corners with four equivalent GeSe4 tetrahedra, and edges with two equivalent NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 12–91°. There are two shorter (2.70 Å) and two longer (2.79 Å) Ag–Se bond lengths. Ge4+ is bonded to four Se2- atoms to form GeSe4 tetrahedra that share corners with two NaSe6 octahedra, a cornercorner with one GeSe4 tetrahedra, corners with two equivalent AgSe4 tetrahedra, and edges with four NaSe6 octahedra. The corner-sharing octahedra tilt angles range from 16–66°. There are three shorter (2.37 Å) and one longer (2.44 Å) Ge–Se bond lengths. There are four inequivalent Se2- sites. In the first Se2- site, Se2- is bonded to three Na1+, one Ag1+, and one Ge4+ atom to form distorted SeNa3AgGe trigonal bipyramids that share corners with seven SeNa5Ge octahedra, corners with two equivalent SeNa3AgGe trigonal bipyramids, and edges with four SeNa5Ge octahedra. The corner-sharing octahedra tilt angles range from 20–77°. In the second Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent Na1+ and two equivalent Ge4+ atoms. In the third Se2- site, Se2- is bonded to four Na1+, one Ag1+, and one Ge4+ atom to form SeNa4AgGe octahedra that share corners with three SeNa5Ge octahedra, corners with two equivalent SeNa3AgGe trigonal bipyramids, edges with five SeNa5Ge octahedra, and edges with three equivalent SeNa3AgGe trigonal bipyramids. The corner-sharing octahedra tilt angles range from 0–70°. In the fourth Se2- site, Se2- is bonded to five Na1+ and one Ge4+ atom to form SeNa5Ge octahedra that share corners with two SeNa5Ge octahedra, corners with five equivalent SeNa3AgGe trigonal bipyramids, edges with six SeNa5Ge octahedra, and an edgeedge with one SeNa3AgGe trigonal bipyramid. The corner-sharing octahedra tilt angles range from 0–12°.