DOE OSTI2020
Ca3Bi2(AsO6)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with three AsO4 tetrahedra, edges with two equivalent CaO7 pentagonal bipyramids, an edgeedge with one AsO4 tetrahedra, and a faceface with one CaO7 pentagonal bipyramid. There are a spread of Ca–O bond distances ranging from 2.31–2.76 Å. In the second Ca2+ site, Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with four equivalent CaO7 pentagonal bipyramids, corners with three AsO4 tetrahedra, an edgeedge with one AsO4 tetrahedra, and a faceface with one CaO7 pentagonal bipyramid. There are a spread of Ca–O bond distances ranging from 2.30–2.72 Å. In the third Ca2+ site, Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with four equivalent CaO7 pentagonal bipyramids, corners with three AsO4 tetrahedra, edges with two equivalent CaO7 pentagonal bipyramids, and an edgeedge with one AsO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.40–2.74 Å. There are two inequivalent Bi4+ sites. In the first Bi4+ site, Bi4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Bi–O bond distances ranging from 2.14–2.64 Å. In the second Bi4+ site, Bi4+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of Bi–O bond distances ranging from 2.17–2.47 Å. There are two inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with five CaO7 pentagonal bipyramids and an edgeedge with one CaO7 pentagonal bipyramid. There are a spread of As–O bond distances ranging from 1.72–1.74 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four CaO7 pentagonal bipyramids and edges with two CaO7 pentagonal bipyramids. There are a spread of As–O bond distances ranging from 1.72–1.75 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to two Ca2+ and two Bi4+ atoms to form distorted edge-sharing OCa2Bi2 tetrahedra. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Bi4+, and one As5+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ca2+ and two Bi4+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one As5+ atom. In the sixth O2- site, O2- is bonded in a trigonal non-coplanar geometry to one Ca2+ and two Bi4+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Bi4+, and one As5+ atom. In the eighth O2- site, O2- is bonded to two Ca2+ and two Bi4+ atoms to form edge-sharing OCa2Bi2 tetrahedra. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Ca2+, one Bi4+, and one As5+ atom. In the eleventh O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one As5+ atom. In the twelfth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one As5+ atom.