DOI: 10.17188/1263233
title: Materials Data on Ca3(AsO4)2 by Materials Project

description: Ca3(AsO4)2 crystallizes in the trigonal R3 space group. The structure is three-dimensional. there are nine inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six AsO4 tetrahedra and edges with three equivalent CaO7 pentagonal bipyramids. There are three shorter (2.29 Å) and three longer (2.32 Å) Ca–O bond lengths. In the second Ca2+ site, Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent CaO7 pentagonal bipyramids, corners with five AsO4 tetrahedra, an edgeedge with one CaO6 octahedra, and an edgeedge with one AsO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.65 Å. In the third Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.37–2.93 Å. In the fourth Ca2+ site, Ca2+ is bonded to seven O2- atoms to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent CaO7 pentagonal bipyramids, corners with five AsO4 tetrahedra, an edgeedge with one CaO6 octahedra, and an edgeedge with one AsO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.34–2.54 Å. In the fifth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.91 Å. In the sixth Ca2+ site, Ca2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ca–O bond distances ranging from 2.43–2.99 Å. In the seventh Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are three shorter (2.41 Å) and three longer (2.71 Å) Ca–O bond lengths. In the eighth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.39–2.91 Å. In the ninth Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with six AsO4 tetrahedra and edges with three equivalent CaO7 pentagonal bipyramids. There are three shorter (2.31 Å) and three longer (2.34 Å) Ca–O bond lengths. There are six inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three equivalent CaO7 pentagonal bipyramids. There is three shorter (1.72 Å) and one longer (1.74 Å) As–O bond length. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with three CaO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 60°. There are a spread of As–O bond distances ranging from 1.71–1.73 Å. In the third As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with three CaO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 60°. There is two shorter (1.71 Å) and two longer (1.72 Å) As–O bond length. In the fourth As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three equivalent CaO7 pentagonal bipyramids. There is one shorter (1.70 Å) and three longer (1.74 Å) As–O bond length. In the fifth As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one CaO7 pentagonal bipyramid, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 46°. There are a spread of As–O bond distances ranging from 1.70–1.74 Å. In the sixth As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one CaO7 pentagonal bipyramid, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 56°. There is two shorter (1.71 Å) and two longer (1.74 Å) As–O bond length. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent Ca2+ and one As5+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to three Ca2+ and one As5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one As5+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one As5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one As5+ atom. In the seventh O2- site, O2- is bonded in a distorted tetrahedral geometry to three Ca2+ and one As5+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom. 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 4-coordinate geometry to three equivalent Ca2+ and one As5+ atom. In the eleventh O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom. In the thirteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Ca2+ and one As5+ atom. In the fifteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one As5+ atom. In the sixteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Ca2+ and one As5+ atom. In the seventeenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one As5+ atom. In the eighteenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one As5+ atom. In the nineteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one As5+ atom. In the twentieth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one As5+ atom.