DOE OSTI2020
Ca(SnO2)2 is beta indium sulfide-derived structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are eight inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 53–65°. There are a spread of Ca–O bond distances ranging from 2.26–2.56 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with three CaO4 tetrahedra and edges with four equivalent SnO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.30–2.41 Å. In the third Ca2+ site, Ca2+ is bonded to four O2- atoms to form CaO4 tetrahedra that share corners with three CaO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 52–67°. There are a spread of Ca–O bond distances ranging from 2.25–2.52 Å. In the fourth Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with two equivalent CaO4 tetrahedra, corners with three SnO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with four equivalent SnO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.41 Å. In the fifth Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with five SnO4 tetrahedra, edges with two CaO6 octahedra, and edges with four equivalent SnO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.43 Å. In the sixth Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with six SnO4 tetrahedra, edges with two CaO6 octahedra, and edges with four SnO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.41–2.47 Å. In the seventh Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share a cornercorner with one CaO4 tetrahedra, a cornercorner with one SnO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with four equivalent SnO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.32–2.40 Å. In the eighth Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with three equivalent SnO4 tetrahedra, edges with two CaO6 octahedra, and edges with four SnO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.37–2.47 Å. There are twelve inequivalent Sn3+ sites. In the first Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with three CaO4 tetrahedra, edges with two equivalent CaO6 octahedra, and edges with two equivalent SnO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.07–2.19 Å. In the second Sn3+ site, Sn3+ is bonded in a 6-coordinate geometry to three O2- atoms. There are two shorter (2.24 Å) and one longer (2.32 Å) Sn–O bond lengths. In the third Sn3+ site, Sn3+ is bonded to four O2- atoms to form distorted SnO4 tetrahedra that share corners with six CaO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 52–74°. There are a spread of Sn–O bond distances ranging from 2.14–2.80 Å. In the fourth Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with two equivalent CaO4 tetrahedra, corners with three SnO4 tetrahedra, edges with two equivalent SnO6 octahedra, and edges with three CaO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.08–2.22 Å. In the fifth Sn3+ site, Sn3+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are two shorter (2.09 Å) and one longer (2.32 Å) Sn–O bond lengths. In the sixth Sn3+ site, Sn3+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are two shorter (2.13 Å) and one longer (2.59 Å) Sn–O bond lengths. In the seventh Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with five SnO4 tetrahedra, edges with two equivalent SnO6 octahedra, and edges with four CaO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.10–2.15 Å. In the eighth Sn3+ site, Sn3+ is bonded to four O2- atoms to form distorted SnO4 tetrahedra that share corners with six CaO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 51–74°. There are a spread of Sn–O bond distances ranging from 2.15–2.74 Å. In the ninth Sn3+ site, Sn3+ is bonded to six O2- atoms to form SnO6 octahedra that share a cornercorner with one CaO4 tetrahedra, a cornercorner with one SnO4 tetrahedra, edges with two equivalent SnO6 octahedra, and edges with three CaO6 octahedra. There are a spread of Sn–O bond distances ranging from 2.10–2.19 Å. In the tenth Sn3+ site, Sn3+ is bonded to four O2- atoms to form distorted SnO4 tetrahedra that share corners with six CaO6 octahedra and corners with six SnO6 octahedra. The corner-sharing octahedra tilt angles range from 51–75°. There are a spread of Sn–O bond distances ranging from 2.15–2.76 Å. In the eleventh Sn3+ site, Sn3+ is bonded in a 6-coordinate geometry to three O2- atoms. There are two shorter (2.24 Å) and one longer (2.28 Å) Sn–O bond lengths. In the twelfth Sn3+ site, Sn3+ is bonded in a trigonal non-coplanar geometry to three O2- atoms. There are two shorter (2.09 Å) and one longer (2.34 Å) Sn–O bond lengths. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded to two Ca2+ and two Sn3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Sn2 tetrahedra. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two equivalent Sn3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Sn3+ atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to three Sn3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+ and two Sn3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Sn3+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and three Sn3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ca2+ and two equivalent Sn3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Ca2+ and three Sn3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+ and two Sn3+ atoms. In the eleventh O2- site, O2- is bonded to one Ca2+ and three Sn3+ atoms to form distorted OCaSn3 trigonal pyramids that share corners with three OCaSn3 tetrahedra and edges with two equivalent OCa2Sn2 tetrahedra. In the twelfth O2- site, O2- is bonded to two Ca2+ and two Sn3+ atoms to form distorted OCa2Sn2 tetrahedra that share corners with two OCaSn3 tetrahedra, a cornercorner with one OCaSn3 trigonal pyramid, an edgeedge with one OCa2Sn2 tetrahedra, and an edgeedge with one OCaSn3 trigonal pyramid. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two equivalent Sn3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ca2+ and two equivalent Sn3+ atoms. In the fifteenth O2- site, O2- is bonded to one Ca2+ and three Sn3+ atoms to form distorted corner-sharing OCaSn3 tetrahedra. In the sixteenth O2- site, O2- is bonded to one Ca2+ and three Sn3+ atoms to form distorted OCaSn3 tetrahedra that share corners with seven OCaSn3 tetrahedra and edges with two equivalent OCa2Sn2 tetrahedra. In the seventeenth O2- site, O2- is bonded to two Ca2+ and two Sn3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Sn2 tetrahedra. In the eighteenth O2- site, O2- is bonded to two Ca2+ and two Sn3+ atoms to form a mixture of distorted edge and corner-sharing OCa2Sn2 tetrahedra. In the nineteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+ and two equivalent Sn3+ atoms. In the twentieth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Sn3+ atoms. In the twenty-first O2- site, O2- is bonded to one Ca2+ and three Sn3+ atoms to form distorted OCaSn3 tetrahedra that share corners with five OCaSn3 tetrahedra and edges with two equivalent OCa2Sn2 tetrahedra. In the twenty-second O2- site, O2- is bonded in a 3-coordinate geometry to three Sn3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Sn3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Sn3+ atoms.