K2Al2(SiO4)3 crystallizes in the orthorhombic Fdd2 space group. K(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), two equivalent O(2), and two equivalent O(6) atoms. Al(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with three equivalent Si(2)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(1) and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with three equivalent Al(1)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Al(1), and one Si(2) atom. In the second O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Al(1), and one Si(2) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent K(1) atoms. In the fifth O site, O(1) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the sixth O site, O(2) is bonded in a 4-coordinate geometry to two equivalent K(1), one Al(1), and one Si(2) atom.
K2Al2(SiO4)3 crystallizes in the orthorhombic Fdd2 space group. K(1) is bonded in a 6-coordinate geometry to one O(3), one O(4), two equivalent O(2), and two equivalent O(6) atoms. The K(1)-O(3) bond length is 2.71 Å. The K(1)-O(4) bond length is 2.71 Å. There is one shorter (2.75 Å) and one longer (2.76 Å) K(1)-O(2) bond length. There is one shorter (3.04 Å) and one longer (3.13 Å) K(1)-O(6) bond length. Al(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form AlO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with three equivalent Si(2)O4 tetrahedra. The Al(1)-O(1) bond length is 1.77 Å. The Al(1)-O(2) bond length is 1.76 Å. The Al(1)-O(3) bond length is 1.75 Å. The Al(1)-O(4) bond length is 1.76 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(1) and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. Both Si(1)-O(1) bond lengths are 1.64 Å. Both Si(1)-O(5) bond lengths are 1.64 Å. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with three equivalent Al(1)O4 tetrahedra. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(3) bond length is 1.63 Å. The Si(2)-O(4) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.65 Å. There are six inequivalent O sites. In the first O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Al(1), and one Si(2) atom. In the second O site, O(4) is bonded in a 3-coordinate geometry to one K(1), one Al(1), and one Si(2) atom. In the third O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the fourth O site, O(6) is bonded in a 2-coordinate geometry to two equivalent K(1) atoms. In the fifth O site, O(1) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the sixth O site, O(2) is bonded in a 4-coordinate geometry to two equivalent K(1), one Al(1), and one Si(2) atom.