Materials Data on CaGeO3 by Materials Project
CaGeO3 crystallizes in the triclinic P-1 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 four GeO4 tetrahedra, edges with four CaO6 octahedra, edges with two equivalent CaO7 pentagonal bipyramids, and edges with two GeO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.36–2.56 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with five GeO4 tetrahedra, edges with two equivalent CaO6 octahedra, edges with two equivalent CaO7 pentagonal bipyramids, and an edgeedge with one GeO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.53 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with five GeO4 tetrahedra, edges with two equivalent CaO6 octahedra, edges with two equivalent CaO7 pentagonal bipyramids, and an edgeedge with one GeO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.61 Å. There are three inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with four CaO6 octahedra, a cornercorner with one CaO7 pentagonal bipyramid, corners with two GeO4 tetrahedra, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 49–62°. There are a spread of Ge–O bond distances ranging from 1.74–1.80 Å. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with four CaO6 octahedra, a cornercorner with one CaO7 pentagonal bipyramid, corners with two GeO4 tetrahedra, and an edgeedge with one CaO7 pentagonal bipyramid. The corner-sharing octahedra tilt angles range from 46–62°. There are a spread of Ge–O bond distances ranging from 1.72–1.81 Å. In the third Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two CaO6 octahedra, corners with two equivalent CaO7 pentagonal bipyramids, corners with two GeO4 tetrahedra, and edges with two CaO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Ge–O bond distances ranging from 1.74–1.82 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+ and two Ge4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ca2+ and one Ge4+ atom. In the third O2- site, O2- is bonded in a trigonal planar geometry to two Ca2+ and one Ge4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Ge4+ atoms. In the fifth O2- site, O2- is bonded to three Ca2+ and one Ge4+ atom to form distorted edge-sharing OCa3Ge trigonal pyramids. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Ge4+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Ge4+ atom. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Ge4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Ge4+ atom.