BaSiO3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form BaO8 hexagonal bipyramids that share corners with two equivalent Ba(2)O8 hexagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, edges with six equivalent Ba(2)O8 hexagonal bipyramids, edges with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Si(2)O4 tetrahedra. In the second Ba site, Ba(2) is bonded to one O(3), one O(5), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted BaO8 hexagonal bipyramids that share  a cornercorner with one Ba(1)O8 hexagonal bipyramid,  a cornercorner with one Ba(2)O8 hexagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, edges with three equivalent Ba(1)O8 hexagonal bipyramids, edges with three equivalent Ba(2)O8 hexagonal bipyramids,  an edgeedge with one Si(2)O4 tetrahedra, and edges with three equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Ba(1)O8 hexagonal bipyramid,  a cornercorner with one Ba(2)O8 hexagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Ba(1)O8 hexagonal bipyramid, and edges with three equivalent Ba(2)O8 hexagonal bipyramids. In the second Si site, Si(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with two equivalent Ba(2)O8 hexagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Ba(1)O8 hexagonal bipyramids, and edges with two equivalent Ba(2)O8 hexagonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(2), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Ba(2) and two equivalent Si(1) atoms.
BaSiO3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form BaO8 hexagonal bipyramids that share corners with two equivalent Ba(2)O8 hexagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, edges with six equivalent Ba(2)O8 hexagonal bipyramids, edges with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Si(2)O4 tetrahedra. Both Ba(1)-O(1) bond lengths are 2.85 Å. Both Ba(1)-O(2) bond lengths are 2.72 Å. Both Ba(1)-O(3) bond lengths are 2.85 Å. Both Ba(1)-O(4) bond lengths are 2.83 Å. In the second Ba site, Ba(2) is bonded to one O(3), one O(5), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted BaO8 hexagonal bipyramids that share  a cornercorner with one Ba(1)O8 hexagonal bipyramid,  a cornercorner with one Ba(2)O8 hexagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, edges with three equivalent Ba(1)O8 hexagonal bipyramids, edges with three equivalent Ba(2)O8 hexagonal bipyramids,  an edgeedge with one Si(2)O4 tetrahedra, and edges with three equivalent Si(1)O4 tetrahedra. The Ba(2)-O(3) bond length is 2.84 Å. The Ba(2)-O(5) bond length is 2.85 Å. There is one shorter (2.68 Å) and one longer (2.83 Å) Ba(2)-O(1) bond length. Both Ba(2)-O(2) bond lengths are 2.90 Å. There is one shorter (2.67 Å) and one longer (2.83 Å) Ba(2)-O(4) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Ba(1)O8 hexagonal bipyramid,  a cornercorner with one Ba(2)O8 hexagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra,  an edgeedge with one Ba(1)O8 hexagonal bipyramid, and edges with three equivalent Ba(2)O8 hexagonal bipyramids. The Si(1)-O(1) bond length is 1.60 Å. The Si(1)-O(2) bond length is 1.60 Å. The Si(1)-O(3) bond length is 1.68 Å. The Si(1)-O(5) bond length is 1.68 Å. In the second Si site, Si(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form SiO4 tetrahedra that share corners with two equivalent Ba(2)O8 hexagonal bipyramids, corners with two equivalent Si(1)O4 tetrahedra, edges with two equivalent Ba(1)O8 hexagonal bipyramids, and edges with two equivalent Ba(2)O8 hexagonal bipyramids. Both Si(2)-O(3) bond lengths are 1.67 Å. Both Si(2)-O(4) bond lengths are 1.60 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Si(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Si(1) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(2), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Si(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to two equivalent Ba(2) and two equivalent Si(1) atoms.