Materials Data on Ca3W2O9 by Materials Project
Ca3W2O9 crystallizes in the orthorhombic Pna2_1 space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two equivalent CaO6 octahedra, corners with four WO4 tetrahedra, edges with two equivalent CaO6 octahedra, and edges with two equivalent CaO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 54°. There are a spread of Ca–O bond distances ranging from 2.20–2.50 Å. In the second Ca2+ site, Ca2+ is bonded to five O2- atoms to form distorted CaO5 trigonal bipyramids that share corners with four WO4 tetrahedra and edges with three CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.17–2.47 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with five WO4 tetrahedra, edges with two equivalent CaO6 octahedra, and an edgeedge with one CaO5 trigonal bipyramid. There are a spread of Ca–O bond distances ranging from 2.24–2.79 Å. There are two inequivalent W6+ sites. In the first W6+ site, W6+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with five CaO6 octahedra and corners with two equivalent CaO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 46–51°. There are a spread of W–O bond distances ranging from 1.79–1.83 Å. In the second W6+ site, W6+ is bonded to four O2- atoms to form WO4 tetrahedra that share corners with four CaO6 octahedra and corners with two equivalent CaO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 10–52°. There are a spread of W–O bond distances ranging from 1.80–1.84 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one Ca2+ and one W6+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one W6+ atom. In the third O2- site, O2- is bonded to four Ca2+ atoms to form corner-sharing OCa4 tetrahedra. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to two Ca2+ and one W6+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one W6+ atom. In the sixth O2- site, O2- is bonded in a linear geometry to one Ca2+ and one W6+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Ca2+ and one W6+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one W6+ atom. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one W6+ atom.