DOE OSTI2020
BaGe2O5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.76–3.37 Å. In the second Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.64–3.03 Å. In the third Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.67–3.26 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 1-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.51–3.21 Å. There are nine inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four O2- atoms to form corner-sharing GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–68°. There are a spread of Ge–O bond distances ranging from 1.72–1.84 Å. In the second Ge4+ site, Ge4+ is bonded to six O2- atoms to form GeO6 octahedra that share a cornercorner with one GeO6 octahedra, corners with three GeO4 tetrahedra, a cornercorner with one GeO5 trigonal bipyramid, and an edgeedge with one GeO6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of Ge–O bond distances ranging from 1.86–2.09 Å. In the third Ge4+ site, Ge4+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ge–O bond distances ranging from 1.86–2.47 Å. In the fourth Ge4+ site, Ge4+ is bonded to four O2- atoms to form corner-sharing GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 61–65°. There is three shorter (1.77 Å) and one longer (1.78 Å) Ge–O bond length. In the fifth Ge4+ site, Ge4+ is bonded to six O2- atoms to form GeO6 octahedra that share a cornercorner with one GeO6 octahedra, corners with two GeO4 tetrahedra, and corners with two equivalent GeO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 40°. There are a spread of Ge–O bond distances ranging from 1.91–1.97 Å. In the sixth Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with three GeO6 octahedra and a cornercorner with one GeO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 40–62°. There are a spread of Ge–O bond distances ranging from 1.74–1.82 Å. In the seventh Ge4+ site, Ge4+ is bonded to five O2- atoms to form GeO5 trigonal bipyramids that share corners with three GeO6 octahedra and a cornercorner with one GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 44–59°. There are a spread of Ge–O bond distances ranging from 1.80–2.13 Å. In the eighth Ge4+ site, Ge4+ is bonded to six O2- atoms to form GeO6 octahedra that share corners with four GeO4 tetrahedra and edges with two equivalent GeO6 octahedra. There are a spread of Ge–O bond distances ranging from 1.84–2.19 Å. In the ninth Ge4+ site, Ge4+ is bonded to six O2- atoms to form corner-sharing GeO6 octahedra. There are a spread of Ge–O bond distances ranging from 1.89–2.04 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Ge4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Ge4+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to three Ba2+ and two Ge4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two Ge4+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+ and two Ge4+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Ge4+ atoms. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to three Ba2+ and two Ge4+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Ge4+ atoms. In the ninth O2- site, O2- is bonded in a 1-coordinate geometry to two Ba2+ and two Ge4+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ba2+ and two Ge4+ atoms. In the eleventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ba2+ and two Ge4+ atoms. In the twelfth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ba2+ and two Ge4+ atoms. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+ and three Ge4+ atoms. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to three Ge4+ atoms. In the fifteenth O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+ and two Ge4+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ba2+ and two Ge4+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two Ba2+ and two Ge4+ atoms. In the eighteenth O2- site, O2- is bonded to two Ba2+ and two Ge4+ atoms to form distorted corner-sharing OBa2Ge2 tetrahedra. In the nineteenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ba2+ and one Ge4+ atom. In the twentieth O2- site, O2- is bonded in a 4-coordinate geometry to two Ba2+ and two Ge4+ atoms.