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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ca2GeO4 by Materials Project

Ca2GeO4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ca2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ca–O bond distances ranging from 2.27–2.69 Å. Ge4+ is bonded to six O2- atoms to form corner-sharing GeO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There is four shorter (1.90 Å) and two longer (1.91 Å) Ge–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Ca2+ and two equivalent Ge4+ atoms to form a mixture of distorted corner, edge, and face-sharing OCa4Ge2 octahedra. The corner-sharing octahedra tilt angles range from 0–55°. In the second O2- site, O2- is bonded to five equivalent Ca2+ and one Ge4+ atom to form distorted OCa5Ge octahedra that share corners with seventeen OCa4Ge2 octahedra, edges with eight equivalent OCa5Ge octahedra, and faces with four equivalent OCa4Ge2 octahedra. The corner-sharing octahedra tilt angles range from 0–55°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2GeO4 by Materials Project

Ca2GeO4 is Spinel-like structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with eight CaO6 octahedra, corners with four equivalent GeO4 tetrahedra, edges with two equivalent CaO6 octahedra, and an edgeedge with one GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–67°. There are a spread of Ca–O bond distances ranging from 2.32–2.48 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with four equivalent CaO6 octahedra, corners with two equivalent GeO4 tetrahedra, edges with four CaO6 octahedra, and edges with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 59–67°. There are a spread of Ca–O bond distances ranging from 2.35–2.43 Å. Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with six CaO6 octahedra and edges with three CaO6 octahedra. The corner-sharing octahedra tilt angles range from 54–62°. There are a spread of Ge–O bond distances ranging from 1.77–1.81 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Ca2+ and one Ge4+ atom. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Ca2+ and one Ge4+ atom. In the third O2- site, O2- is bonded to three Ca2+ and one Ge4+ atom to form distorted corner-sharing OCa3Ge trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ca2GeO4 by Materials Project

Ca2GeO4 crystallizes in the trigonal P-3m1 space group. The structure is three-dimensional. there are three inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a distorted single-bond geometry to ten O2- atoms. There are a spread of Ca–O bond distances ranging from 2.08–2.94 Å. In the second Ca2+ site, Ca2+ is bonded to six equivalent O2- atoms to form CaO6 octahedra that share corners with six equivalent GeO4 tetrahedra. All Ca–O bond lengths are 2.23 Å. In the third Ca2+ site, Ca2+ is bonded in a distorted hexagonal planar geometry to six equivalent O2- atoms. All Ca–O bond lengths are 2.67 Å. Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three equivalent CaO6 octahedra. The corner-sharing octahedral tilt angles are 14°. There is one shorter (1.71 Å) and three longer (1.78 Å) Ge–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to one Ca2+ and one Ge4+ atom. In the second O2- site, O2- is bonded in a 6-coordinate geometry to five Ca2+ and one Ge4+ atom.

36 MATERIALS SCIENCE↗