DOE OSTI2020
Ga10Si2O19 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are eight inequivalent Ga3+ sites. In the first Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with four equivalent GaO6 octahedra and corners with three GaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–61°. There is two shorter (1.85 Å) and two longer (1.86 Å) Ga–O bond length. In the second Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with four GaO6 octahedra, corners with three GaO4 tetrahedra, and a cornercorner with one GaO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 61–66°. There are a spread of Ga–O bond distances ranging from 1.81–2.01 Å. In the third Ga3+ site, Ga3+ is bonded to four O2- atoms to form distorted GaO4 tetrahedra that share corners with four GaO6 octahedra, corners with two equivalent SiO4 tetrahedra, a cornercorner with one GaO5 trigonal bipyramid, and a cornercorner with one SiO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 50–70°. There are a spread of Ga–O bond distances ranging from 1.78–1.97 Å. In the fourth Ga3+ site, Ga3+ is bonded to five O2- atoms to form GaO5 trigonal bipyramids that share corners with two equivalent GaO6 octahedra, corners with two GaO4 tetrahedra, corners with two equivalent SiO5 trigonal bipyramids, edges with two equivalent GaO6 octahedra, and an edgeedge with one SiO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 51°. There are a spread of Ga–O bond distances ranging from 1.93–2.07 Å. In the fifth Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share a cornercorner with one SiO4 tetrahedra, corners with three GaO4 tetrahedra, a cornercorner with one GaO5 trigonal bipyramid, a cornercorner with one SiO5 trigonal bipyramid, edges with two equivalent GaO6 octahedra, an edgeedge with one GaO5 trigonal bipyramid, and an edgeedge with one SiO5 trigonal bipyramid. There are a spread of Ga–O bond distances ranging from 1.95–2.06 Å. In the sixth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with four GaO6 octahedra, a cornercorner with one SiO4 tetrahedra, and corners with three GaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–57°. There are a spread of Ga–O bond distances ranging from 1.82–1.95 Å. In the seventh Ga3+ site, Ga3+ is bonded to six O2- atoms to form GaO6 octahedra that share a cornercorner with one SiO4 tetrahedra, corners with seven GaO4 tetrahedra, and edges with two equivalent GaO6 octahedra. There are a spread of Ga–O bond distances ranging from 1.95–2.14 Å. In the eighth Ga3+ site, Ga3+ is bonded to four O2- atoms to form GaO4 tetrahedra that share corners with four equivalent GaO6 octahedra, a cornercorner with one SiO4 tetrahedra, and corners with three GaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–62°. There is three shorter (1.81 Å) and one longer (2.02 Å) Ga–O bond length. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to five O2- atoms to form SiO5 trigonal bipyramids that share corners with two equivalent GaO6 octahedra, a cornercorner with one GaO4 tetrahedra, corners with two equivalent GaO5 trigonal bipyramids, edges with two equivalent GaO6 octahedra, and an edgeedge with one GaO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 51°. There are a spread of Si–O bond distances ranging from 1.70–1.98 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four GaO6 octahedra and corners with four GaO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–60°. There is one shorter (1.61 Å) and three longer (1.69 Å) Si–O bond length. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Ga3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two Ga3+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Ga3+ atoms. In the fourth O2- site, O2- is bonded to four Ga3+ atoms to form distorted corner-sharing OGa4 tetrahedra. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to two Ga3+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Ga3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded to three Ga3+ and one Si4+ atom to form corner-sharing OGa3Si trigonal pyramids. In the eighth O2- site, O2- is bonded in a distorted T-shaped geometry to two Ga3+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a trigonal planar geometry to two Ga3+ and one Si4+ atom. In the tenth O2- site, O2- is bonded in a trigonal planar geometry to three Ga3+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ga3+ and one Si4+ atom. In the twelfth O2- site, O2- is bonded in a trigonal planar geometry to three Ga3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ga3+ and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a trigonal planar geometry to three Ga3+ atoms. In the fifteenth O2- site, O2- is bonded in a trigonal planar geometry to three Ga3+ atoms.