Materials Data on Ca10Mg2Sb9 by Materials Project
Ca10Mg2Sb9 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six Sb+2.67- atoms to form distorted CaSb6 octahedra that share corners with four equivalent CaSb6 octahedra, corners with seven equivalent CaSb7 pentagonal bipyramids, corners with two equivalent MgSb4 tetrahedra, edges with two equivalent CaSb6 octahedra, faces with two equivalent CaSb6 octahedra, and faces with three equivalent CaSb7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 26–50°. There are a spread of Ca–Sb bond distances ranging from 3.12–3.45 Å. In the second Ca2+ site, Ca2+ is bonded to seven Sb+2.67- atoms to form distorted CaSb7 pentagonal bipyramids that share corners with seven equivalent CaSb6 octahedra, corners with three equivalent CaSb7 pentagonal bipyramids, a cornercorner with one MgSb4 tetrahedra, edges with two equivalent CaSb7 pentagonal bipyramids, an edgeedge with one MgSb4 tetrahedra, faces with three equivalent CaSb6 octahedra, and faces with four equivalent CaSb7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 34–53°. There are a spread of Ca–Sb bond distances ranging from 3.14–3.69 Å. In the third Ca2+ site, Ca2+ is bonded in a 4-coordinate geometry to four Sb+2.67- atoms. There are two shorter (3.22 Å) and two longer (3.28 Å) Ca–Sb bond lengths. In the fourth Ca2+ site, Ca2+ is bonded in a 5-coordinate geometry to five Sb+2.67- atoms. There are a spread of Ca–Sb bond distances ranging from 3.13–3.51 Å. There are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded in a see-saw-like geometry to four Sb+2.67- atoms. There are two shorter (2.97 Å) and two longer (3.10 Å) Mg–Sb bond lengths. In the second Mg2+ site, Mg2+ is bonded to four Sb+2.67- atoms to form MgSb4 tetrahedra that share corners with eight equivalent CaSb6 octahedra, corners with four equivalent CaSb7 pentagonal bipyramids, edges with four equivalent CaSb7 pentagonal bipyramids, and an edgeedge with one MgSb4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–59°. There are two shorter (2.88 Å) and two longer (2.89 Å) Mg–Sb bond lengths. There are six inequivalent Sb+2.67- sites. In the first Sb+2.67- site, Sb+2.67- is bonded in a 9-coordinate geometry to seven Ca2+, one Mg2+, and one Sb+2.67- atom. The Sb–Sb bond length is 3.08 Å. In the second Sb+2.67- site, Sb+2.67- is bonded in a 6-coordinate geometry to four equivalent Ca2+ and two equivalent Mg2+ atoms. In the third Sb+2.67- site, Sb+2.67- is bonded in a 2-coordinate geometry to seven Ca2+ and one Sb+2.67- atom. In the fourth Sb+2.67- site, Sb+2.67- is bonded in a 7-coordinate geometry to seven Ca2+ atoms. In the fifth Sb+2.67- site, Sb+2.67- is bonded in a 8-coordinate geometry to eight Ca2+ atoms. In the sixth Sb+2.67- site, Sb+2.67- is bonded in a 9-coordinate geometry to seven Ca2+ and two Mg2+ atoms.