SrCaAl4(SiO5)4 crystallizes in the monoclinic Pm space group. Sr(1) is bonded in a 6-coordinate geometry to one O(3), one O(7), two equivalent O(12), and two equivalent O(6) atoms. Ca(1) is bonded in a 6-coordinate geometry to one O(4), one O(8), two equivalent O(11), and two equivalent O(5) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(10), one O(11), one O(12), one O(2), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Al(2)O6 octahedra. In the second Al site, Al(2) is bonded to one O(1), one O(10), one O(2), one O(5), one O(6), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Al(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(11), one O(5), one O(8), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-60°. In the second Si site, Si(2) is bonded to one O(10), one O(12), one O(6), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-59°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one Al(1) and one Al(2) atom. In the second O site, O(2) is bonded in a water-like geometry to one Al(1) and one Al(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Sr(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Ca(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(2), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Sr(1) and two equivalent Si(2) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(1) and two equivalent Si(1) atoms. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one Si(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one Si(2) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Ca(1), one Al(1), and one Si(1) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(1), and one Si(2) atom.
SrCaAl4(SiO5)4 crystallizes in the monoclinic Pm space group. Sr(1) is bonded in a 6-coordinate geometry to one O(3), one O(7), two equivalent O(12), and two equivalent O(6) atoms. The Sr(1)-O(3) bond length is 2.67 Å. The Sr(1)-O(7) bond length is 2.65 Å. Both Sr(1)-O(12) bond lengths are 2.48 Å. Both Sr(1)-O(6) bond lengths are 2.53 Å. Ca(1) is bonded in a 6-coordinate geometry to one O(4), one O(8), two equivalent O(11), and two equivalent O(5) atoms. The Ca(1)-O(4) bond length is 2.48 Å. The Ca(1)-O(8) bond length is 2.63 Å. Both Ca(1)-O(11) bond lengths are 2.41 Å. Both Ca(1)-O(5) bond lengths are 2.45 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(1), one O(10), one O(11), one O(12), one O(2), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Al(2)O6 octahedra. The Al(1)-O(1) bond length is 1.90 Å. The Al(1)-O(10) bond length is 2.01 Å. The Al(1)-O(11) bond length is 1.87 Å. The Al(1)-O(12) bond length is 1.86 Å. The Al(1)-O(2) bond length is 1.90 Å. The Al(1)-O(9) bond length is 1.99 Å. In the second Al site, Al(2) is bonded to one O(1), one O(10), one O(2), one O(5), one O(6), and one O(9) atom to form AlO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Al(1)O6 octahedra. The Al(2)-O(1) bond length is 1.90 Å. The Al(2)-O(10) bond length is 2.00 Å. The Al(2)-O(2) bond length is 1.90 Å. The Al(2)-O(5) bond length is 1.89 Å. The Al(2)-O(6) bond length is 1.88 Å. The Al(2)-O(9) bond length is 1.97 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(11), one O(5), one O(8), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-60°. The Si(1)-O(11) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.64 Å. The Si(1)-O(8) bond length is 1.66 Å. The Si(1)-O(9) bond length is 1.65 Å. In the second Si site, Si(2) is bonded to one O(10), one O(12), one O(6), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O6 octahedra, corners with two equivalent Al(2)O6 octahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-59°. The Si(2)-O(10) bond length is 1.65 Å. The Si(2)-O(12) bond length is 1.63 Å. The Si(2)-O(6) bond length is 1.63 Å. The Si(2)-O(7) bond length is 1.67 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a water-like geometry to one Al(1) and one Al(2) atom. In the second O site, O(2) is bonded in a water-like geometry to one Al(1) and one Al(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Sr(1) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Ca(1) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Ca(1), one Al(2), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(2), and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Sr(1) and two equivalent Si(2) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(1) and two equivalent Si(1) atoms. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one Si(1) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Al(1), one Al(2), and one Si(2) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Ca(1), one Al(1), and one Si(1) atom. In the twelfth O site, O(12) is bonded in a distorted trigonal planar geometry to one Sr(1), one Al(1), and one Si(2) atom.