DOI: 10.17188/1704169
title: Materials Data on K2Gd2Sb2Se9 by Materials Project

description: K2Gd2Sb2Se9 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to seven Se2- atoms to form distorted KSe7 pentagonal bipyramids that share a cornercorner with one SeK2Gd2SbSe octahedra, a cornercorner with one KSe7 pentagonal bipyramid, edges with two equivalent SbSe6 octahedra, and faces with two equivalent KSe7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 58°. There are a spread of K–Se bond distances ranging from 3.37–3.42 Å. In the second K1+ site, K1+ is bonded to seven Se2- atoms to form distorted KSe7 pentagonal bipyramids that share a cornercorner with one SeK2Gd2SbSe octahedra, a cornercorner with one KSe7 pentagonal bipyramid, edges with two equivalent SbSe6 octahedra, and faces with two equivalent KSe7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 57°. There are a spread of K–Se bond distances ranging from 3.36–3.45 Å. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Gd–Se bond distances ranging from 2.94–3.09 Å. In the second Gd3+ site, Gd3+ is bonded in a 8-coordinate geometry to eight Se2- atoms. There are a spread of Gd–Se bond distances ranging from 2.93–3.10 Å. There are four inequivalent Sb5+ sites. In the first Sb5+ site, Sb5+ is bonded in a distorted see-saw-like geometry to four Se2- atoms. There are a spread of Sb–Se bond distances ranging from 2.64–3.08 Å. In the second Sb5+ site, Sb5+ is bonded in a distorted see-saw-like geometry to four Se2- atoms. There are a spread of Sb–Se bond distances ranging from 2.63–3.10 Å. In the third Sb5+ site, Sb5+ is bonded to six Se2- atoms to form SbSe6 octahedra that share an edgeedge with one SbSe6 octahedra and edges with four equivalent KSe7 pentagonal bipyramids. There are a spread of Sb–Se bond distances ranging from 2.65–3.11 Å. In the fourth Sb5+ site, Sb5+ is bonded to six Se2- atoms to form SbSe6 octahedra that share an edgeedge with one SbSe6 octahedra and edges with four equivalent KSe7 pentagonal bipyramids. There are a spread of Sb–Se bond distances ranging from 2.66–3.11 Å. There are sixteen inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent K1+, two equivalent Gd3+, and one Se2- atom. The Se–Se bond length is 2.43 Å. In the second Se2- site, Se2- is bonded in a 6-coordinate geometry to two equivalent K1+, two equivalent Gd3+, one Sb5+, and one Se2- atom. The Se–Se bond length is 2.43 Å. In the third Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent K1+, two equivalent Gd3+, and one Se2- atom. The Se–Se bond length is 2.42 Å. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent K1+, two equivalent Gd3+, and one Se2- atom. The Se–Se bond length is 2.42 Å. In the fifth Se2- site, Se2- is bonded in a 6-coordinate geometry to two equivalent K1+, two equivalent Gd3+, one Sb5+, and one Se2- atom. In the sixth Se2- site, Se2- is bonded in a 4-coordinate geometry to two equivalent K1+, two equivalent Gd3+, and one Se2- atom. In the seventh Se2- site, Se2- is bonded to two equivalent K1+, two equivalent Gd3+, one Sb5+, and one Se2- atom to form distorted SeK2Gd2SbSe octahedra that share corners with two equivalent KSe7 pentagonal bipyramids, corners with five SeK2Gd2Sb square pyramids, and edges with two SeK2Gd2Sb square pyramids. In the eighth Se2- site, Se2- is bonded to two equivalent K1+, two equivalent Gd3+, one Sb5+, and one Se2- atom to form distorted SeK2Gd2SbSe octahedra that share corners with two equivalent KSe7 pentagonal bipyramids, corners with five SeK2Gd2Sb square pyramids, and edges with two SeK2Gd2Sb square pyramids. In the ninth Se2- site, Se2- is bonded to two equivalent K1+, two equivalent Gd3+, and one Sb5+ atom to form distorted SeK2Gd2Sb square pyramids that share corners with three SeK2Gd2SbSe octahedra, an edgeedge with one SeK2Gd2SbSe octahedra, and edges with two equivalent SeK2Gd2Sb square pyramids. The corner-sharing octahedra tilt angles range from 3–24°. In the tenth Se2- site, Se2- is bonded to two equivalent K1+, two equivalent Gd3+, and one Sb5+ atom to form SeK2Gd2Sb square pyramids that share corners with four SeK2Gd2SbSe octahedra and edges with two equivalent SeK2Gd2Sb square pyramids. The corner-sharing octahedra tilt angles range from 18–25°. In the eleventh Se2- site, Se2- is bonded to two equivalent K1+, two equivalent Gd3+, and one Sb5+ atom to form distorted SeK2Gd2Sb square pyramids that share corners with two equivalent SeK2Gd2SbSe octahedra, an edgeedge with one SeK2Gd2SbSe octahedra, and edges with two equivalent SeK2Gd2Sb square pyramids. The corner-sharing octahedral tilt angles are 20°. In the twelfth Se2- site, Se2- is bonded to two equivalent K1+, two equivalent Gd3+, and one Sb5+ atom to form distorted SeK2Gd2Sb square pyramids that share a cornercorner with one SeK2Gd2SbSe octahedra, edges with two SeK2Gd2SbSe octahedra, and edges with two equivalent SeK2Gd2Sb square pyramids. The corner-sharing octahedral tilt angles are 4°. In the thirteenth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to two Gd3+ and two Sb5+ atoms. In the fourteenth Se2- site, Se2- is bonded in a distorted rectangular see-saw-like geometry to two Gd3+ and two Sb5+ atoms. In the fifteenth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to two equivalent K1+ and two equivalent Sb5+ atoms. In the sixteenth Se2- site, Se2- is bonded in a rectangular see-saw-like geometry to two equivalent K1+ and two equivalent Sb5+ atoms.