DOE OSTI2020
Ba6Gd(ReO6)3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are four inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, faces with seven BaO12 cuboctahedra, faces with two equivalent GdO6 octahedra, and faces with four ReO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.87–3.06 Å. In the second Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, faces with seven BaO12 cuboctahedra, faces with two equivalent GdO6 octahedra, and faces with four ReO6 octahedra. There are a spread of Ba–O bond distances ranging from 2.86–3.06 Å. In the third Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, corners with three ReO6 octahedra, faces with seven BaO12 cuboctahedra, and faces with three ReO6 octahedra. The corner-sharing octahedra tilt angles range from 21–24°. There are a spread of Ba–O bond distances ranging from 2.95–3.03 Å. In the fourth Ba2+ site, Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with nine BaO12 cuboctahedra, corners with three ReO6 octahedra, faces with seven BaO12 cuboctahedra, a faceface with one GdO6 octahedra, and faces with three ReO6 octahedra. The corner-sharing octahedra tilt angles range from 20–24°. There are a spread of Ba–O bond distances ranging from 2.90–3.04 Å. Gd3+ is bonded to six O2- atoms to form GdO6 octahedra that share corners with six ReO6 octahedra and faces with eight BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. All Gd–O bond lengths are 2.26 Å. There are two inequivalent Re7+ sites. In the first Re7+ site, Re7+ is bonded to six O2- atoms to form ReO6 octahedra that share corners with three BaO12 cuboctahedra, corners with two equivalent GdO6 octahedra, and faces with seven BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Re–O bond distances ranging from 1.84–2.02 Å. In the second Re7+ site, Re7+ is bonded to six O2- atoms to form ReO6 octahedra that share corners with three BaO12 cuboctahedra, corners with two equivalent GdO6 octahedra, and faces with seven BaO12 cuboctahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Re–O bond distances ranging from 1.85–2.01 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom. In the fifth O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom. In the sixth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Gd3+, and one Re7+ atom. In the seventh O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Gd3+, and one Re7+ atom. In the eighth O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom. In the ninth O2- site, O2- is bonded in a distorted linear geometry to four Ba2+, one Gd3+, and one Re7+ atom. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to four Ba2+ and one Re7+ atom.