KBaYSi2O7 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(6), one O(7), two equivalent O(5), and three equivalent O(4) atoms. Ba(1) is bonded in a 9-coordinate geometry to one O(3), one O(6), two equivalent O(1), two equivalent O(7), and three equivalent O(2) atoms. Y(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form YO6 octahedra that share corners with three equivalent 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 one O(2), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with three equivalent Y(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 20-47°. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share corners with three equivalent Y(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-48°. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 5-coordinate geometry to one K(1), two equivalent Ba(1), one Y(1), and one Si(2) atom. In the second O site, O(1) is bonded in a 5-coordinate geometry to one K(1), two equivalent Ba(1), one Y(1), and one Si(2) atom. In the third O site, O(2) is bonded in a 5-coordinate geometry to three equivalent Ba(1), one Y(1), and one Si(1) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Ba(1), one Y(1), and one Si(1) atom. In the fifth O site, O(4) is bonded in a 2-coordinate geometry to three equivalent K(1), one Y(1), and one Si(2) atom. In the sixth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. In the seventh O site, O(6) is bonded in a 2-coordinate geometry to one K(1), one Ba(1), one Y(1), and one Si(1) atom.
KBaYSi2O7 crystallizes in the monoclinic P2_1/c space group. K(1) is bonded in a 9-coordinate geometry to one O(1), one O(3), one O(6), one O(7), two equivalent O(5), and three equivalent O(4) atoms. The K(1)-O(1) bond length is 2.85 Å. The K(1)-O(3) bond length is 3.19 Å. The K(1)-O(6) bond length is 3.09 Å. The K(1)-O(7) bond length is 3.06 Å. There is one shorter (2.79 Å) and one longer (3.13 Å) K(1)-O(5) bond length. There are a spread of K(1)-O(4) bond distances ranging from 2.94-3.08 Å. Ba(1) is bonded in a 9-coordinate geometry to one O(3), one O(6), two equivalent O(1), two equivalent O(7), and three equivalent O(2) atoms. The Ba(1)-O(3) bond length is 2.75 Å. The Ba(1)-O(6) bond length is 2.93 Å. There is one shorter (2.90 Å) and one longer (2.94 Å) Ba(1)-O(1) bond length. There is one shorter (2.80 Å) and one longer (3.09 Å) Ba(1)-O(7) bond length. There are a spread of Ba(1)-O(2) bond distances ranging from 2.86-3.03 Å. Y(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(6), and one O(7) atom to form YO6 octahedra that share corners with three equivalent Si(1)O4 tetrahedra and corners with three equivalent Si(2)O4 tetrahedra. The Y(1)-O(1) bond length is 2.34 Å. The Y(1)-O(2) bond length is 2.34 Å. The Y(1)-O(3) bond length is 2.25 Å. The Y(1)-O(4) bond length is 2.22 Å. The Y(1)-O(6) bond length is 2.26 Å. The Y(1)-O(7) bond length is 2.29 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with three equivalent Y(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 20-47°. The Si(1)-O(2) bond length is 1.65 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.69 Å. The Si(1)-O(6) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share corners with three equivalent Y(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 10-48°. The Si(2)-O(1) bond length is 1.65 Å. The Si(2)-O(4) bond length is 1.63 Å. The Si(2)-O(5) bond length is 1.69 Å. The Si(2)-O(7) bond length is 1.65 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 5-coordinate geometry to one K(1), two equivalent Ba(1), one Y(1), and one Si(2) atom. In the second O site, O(1) is bonded in a 5-coordinate geometry to one K(1), two equivalent Ba(1), one Y(1), and one Si(2) atom. In the third O site, O(2) is bonded in a 5-coordinate geometry to three equivalent Ba(1), one Y(1), and one Si(1) atom. In the fourth O site, O(3) is bonded in a 3-coordinate geometry to one K(1), one Ba(1), one Y(1), and one Si(1) atom. In the fifth O site, O(4) is bonded in a 2-coordinate geometry to three equivalent K(1), one Y(1), and one Si(2) atom. In the sixth O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one Si(1), and one Si(2) atom. In the seventh O site, O(6) is bonded in a 2-coordinate geometry to one K(1), one Ba(1), one Y(1), and one Si(1) atom.