KAl4(SiO6)2 crystallizes in the monoclinic C2/c space group. K(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form KO6 octahedra that share corners with six equivalent Al(1)O4 tetrahedra and corners with six equivalent Si(1)O4 tetrahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form AlO4 tetrahedra that share corners with three equivalent K(1)O6 octahedra and corners with three equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 70-75°. In the second Al site, Al(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share corners with three equivalent K(1)O6 octahedra and corners with three equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-71°. There are six inequivalent O sites. In the first O site, O(2) is bonded in a trigonal planar geometry to one Al(1) and two equivalent Al(2) atoms. In the second O site, O(3) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one Si(1) atom. In the third O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(1), one Al(1), and one Si(1) atom. In the fourth O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one Si(1) atom. In the fifth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Al(2) and one O(6) atom. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Al(2) and one Si(1) atom.
KAl4(SiO6)2 crystallizes in the monoclinic C2/c space group. K(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form KO6 octahedra that share corners with six equivalent Al(1)O4 tetrahedra and corners with six equivalent Si(1)O4 tetrahedra. Both K(1)-O(3) bond lengths are 2.93 Å. Both K(1)-O(4) bond lengths are 3.11 Å. Both K(1)-O(5) bond lengths are 2.90 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form AlO4 tetrahedra that share corners with three equivalent K(1)O6 octahedra and corners with three equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 70-75°. The Al(1)-O(2) bond length is 1.78 Å. The Al(1)-O(3) bond length is 1.75 Å. The Al(1)-O(4) bond length is 1.74 Å. The Al(1)-O(5) bond length is 1.75 Å. In the second Al site, Al(2) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(6) atoms. There is one shorter (1.85 Å) and one longer (1.92 Å) Al(2)-O(1) bond length. There is one shorter (1.80 Å) and one longer (1.86 Å) Al(2)-O(2) bond length. There is one shorter (2.06 Å) and one longer (2.08 Å) Al(2)-O(6) bond length. Si(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share corners with three equivalent K(1)O6 octahedra and corners with three equivalent Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-71°. The Si(1)-O(1) bond length is 1.72 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.62 Å. The Si(1)-O(5) bond length is 1.62 Å. There are six inequivalent O sites. In the first O site, O(2) is bonded in a trigonal planar geometry to one Al(1) and two equivalent Al(2) atoms. In the second O site, O(3) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one Si(1) atom. In the third O site, O(4) is bonded in a distorted bent 150 degrees geometry to one K(1), one Al(1), and one Si(1) atom. In the fourth O site, O(5) is bonded in a 2-coordinate geometry to one K(1), one Al(1), and one Si(1) atom. In the fifth O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Al(2) and one O(6) atom. The O(6)-O(6) bond length is 1.39 Å. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Al(2) and one Si(1) atom.