BaAl2Si3O4N4 crystallizes in the orthorhombic Cmc2_1 space group. Ba(1) is bonded in a 11-coordinate geometry to one N(1), two equivalent N(3), two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AlO4 tetrahedra that share  a cornercorner with one Al(2)N3O tetrahedra,  a cornercorner with one Si(1)N3O tetrahedra, and corners with two equivalent Si(2)N3O tetrahedra. In the second Al site, Al(2) is bonded to one N(2), two equivalent N(3), and one O(3) atom to form AlN3O tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra, corners with two equivalent Si(1)N3O tetrahedra, and corners with four equivalent Si(2)N3O tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(1), two equivalent N(3), and one O(2) atom to form SiN3O tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra, corners with two equivalent Al(2)N3O tetrahedra, and corners with four equivalent Si(2)N3O tetrahedra. In the second Si site, Si(2) is bonded to one N(1), one N(2), one N(3), and one O(1) atom to form SiN3O tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra, corners with two equivalent Al(2)N3O tetrahedra, corners with two equivalent Si(1)N3O tetrahedra, and corners with two equivalent Si(2)N3O tetrahedra. There are three inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one Ba(1), one Si(1), and two equivalent Si(2) atoms. In the second N site, N(2) is bonded in a trigonal planar geometry to one Al(2) and two equivalent Si(2) atoms. In the third N site, N(3) is bonded in a trigonal planar geometry to one Ba(1), one Al(2), one Si(1), and one Si(2) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Al(1), and one Si(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Ba(1), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Ba(1), one Al(1), and one Al(2) atom.
BaAl2Si3O4N4 crystallizes in the orthorhombic Cmc2_1 space group. Ba(1) is bonded in a 11-coordinate geometry to one N(1), two equivalent N(3), two equivalent O(2), two equivalent O(3), and four equivalent O(1) atoms. The Ba(1)-N(1) bond length is 3.38 Å. Both Ba(1)-N(3) bond lengths are 3.15 Å. Both Ba(1)-O(2) bond lengths are 3.19 Å. Both Ba(1)-O(3) bond lengths are 3.40 Å. There are two shorter (2.87 Å) and two longer (2.90 Å) Ba(1)-O(1) bond lengths. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form AlO4 tetrahedra that share  a cornercorner with one Al(2)N3O tetrahedra,  a cornercorner with one Si(1)N3O tetrahedra, and corners with two equivalent Si(2)N3O tetrahedra. The Al(1)-O(2) bond length is 1.75 Å. The Al(1)-O(3) bond length is 1.72 Å. Both Al(1)-O(1) bond lengths are 1.79 Å. In the second Al site, Al(2) is bonded to one N(2), two equivalent N(3), and one O(3) atom to form AlN3O tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra, corners with two equivalent Si(1)N3O tetrahedra, and corners with four equivalent Si(2)N3O tetrahedra. The Al(2)-N(2) bond length is 1.85 Å. Both Al(2)-N(3) bond lengths are 1.86 Å. The Al(2)-O(3) bond length is 1.74 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one N(1), two equivalent N(3), and one O(2) atom to form SiN3O tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra, corners with two equivalent Al(2)N3O tetrahedra, and corners with four equivalent Si(2)N3O tetrahedra. The Si(1)-N(1) bond length is 1.79 Å. Both Si(1)-N(3) bond lengths are 1.73 Å. The Si(1)-O(2) bond length is 1.65 Å. In the second Si site, Si(2) is bonded to one N(1), one N(2), one N(3), and one O(1) atom to form SiN3O tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra, corners with two equivalent Al(2)N3O tetrahedra, corners with two equivalent Si(1)N3O tetrahedra, and corners with two equivalent Si(2)N3O tetrahedra. The Si(2)-N(1) bond length is 1.77 Å. The Si(2)-N(2) bond length is 1.71 Å. The Si(2)-N(3) bond length is 1.73 Å. The Si(2)-O(1) bond length is 1.69 Å. There are three inequivalent N sites. In the first N site, N(1) is bonded in a trigonal planar geometry to one Ba(1), one Si(1), and two equivalent Si(2) atoms. In the second N site, N(2) is bonded in a trigonal planar geometry to one Al(2) and two equivalent Si(2) atoms. In the third N site, N(3) is bonded in a trigonal planar geometry to one Ba(1), one Al(2), one Si(1), and one Si(2) atom. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Al(1), and one Si(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to two equivalent Ba(1), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Ba(1), one Al(1), and one Al(2) atom.