DOE OSTI2020
Sr3CaAl8(SiO5)8 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent Sr sites. In the first Sr site, Sr is bonded in a 6-coordinate geometry to nine O atoms. There are a spread of Sr–O bond distances ranging from 2.51–3.14 Å. In the second Sr site, Sr is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of Sr–O bond distances ranging from 2.50–3.03 Å. Ca is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Ca–O bond distances ranging from 2.40–2.68 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four SiO4 tetrahedra and edges with two AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.01 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four SiO4 tetrahedra and edges with two AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.01 Å. In the third Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four SiO4 tetrahedra and edges with two AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.00 Å. In the fourth Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four SiO4 tetrahedra and edges with two AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.99 Å. There are four inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–58°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Si–O bond distances ranging from 1.63–1.67 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Si–O bond distances ranging from 1.64–1.66 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 48–60°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are twenty-two inequivalent O sites. In the first O site, O is bonded in a water-like geometry to two Al atoms. In the second O site, O is bonded in a water-like geometry to two Al atoms. In the third O site, O is bonded in a water-like geometry to two Al atoms. In the fourth O site, O is bonded in a water-like geometry to two Al atoms. In the fifth O site, O is bonded in a distorted trigonal planar geometry to one Sr, one Al, and one Si atom. In the sixth O site, O is bonded in a distorted trigonal planar geometry to one Sr, one Al, and one Si atom. In the seventh O site, O is bonded in a distorted trigonal planar geometry to one Sr, one Al, and one Si atom. In the eighth O site, O is bonded in a distorted trigonal planar geometry to one Ca, one Al, and one Si atom. In the ninth O site, O is bonded in a distorted single-bond geometry to one Sr atom. In the tenth O site, O is bonded in a distorted single-bond geometry to one Sr and one Ca atom. In the eleventh O site, O is bonded in a distorted bent 150 degrees geometry to two equivalent Sr atoms. In the twelfth O site, O is bonded in a distorted trigonal planar geometry to one Sr, one Al, and one Si atom. In the thirteenth O site, O is bonded in a distorted trigonal planar geometry to one Sr, one Al, and one Si atom. In the fourteenth O site, O is bonded in a distorted trigonal planar geometry to one Sr, one Al, and one Si atom. In the fifteenth O site, O is bonded in a trigonal planar geometry to one Ca, one Al, and one Si atom. In the sixteenth O site, O is bonded in a 3-coordinate geometry to one Sr, two Al, and one Si atom. In the seventeenth O site, O is bonded in a 3-coordinate geometry to one Sr, two Al, and one Si atom. In the eighteenth O site, O is bonded in a 3-coordinate geometry to one Sr, two Al, and one Si atom. In the nineteenth O site, O is bonded in a 3-coordinate geometry to two Al and one Si atom. In the twentieth O site, O is bonded in a distorted bent 150 degrees geometry to one Sr and two equivalent Si atoms. In the twenty-first O site, O is bonded in a distorted bent 150 degrees geometry to one Ca and two equivalent Si atoms. In the twenty-second O site, O is bonded in a distorted bent 150 degrees geometry to one Sr and two Si atoms.