Ba2Sm3Si3SeO12 crystallizes in the hexagonal P6_3/m space group. Ba(1) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. Sm(1) is bonded in a 6-coordinate geometry to two equivalent Se(1), one O(2), one O(3), and four equivalent O(1) atoms. Si(1) is bonded in a tetrahedral geometry to one O(2), one O(3), and two equivalent O(1) atoms. Se(1) is bonded to six equivalent Sm(1) atoms to form SeSm6 octahedra that share corners with six equivalent O(3)Ba2SmSi tetrahedra and faces with two equivalent Se(1)Sm6 octahedra. There are three inequivalent O sites. In the first O site, O(3) is bonded to two equivalent Ba(1), one Sm(1), and one Si(1) atom to form distorted OBa2SmSi tetrahedra that share corners with two equivalent Se(1)Sm6 octahedra and edges with two equivalent O(3)Ba2SmSi tetrahedra. The corner-sharing octahedral tilt angles are 81°. In the second O site, O(1) is bonded in a 1-coordinate geometry to one Ba(1), two equivalent Sm(1), and one Si(1) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Sm(1), and one Si(1) atom.
Ba2Sm3Si3SeO12 crystallizes in the hexagonal P6_3/m space group. Ba(1) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. All Ba(1)-O(1) bond lengths are 2.95 Å. All Ba(1)-O(2) bond lengths are 2.85 Å. All Ba(1)-O(3) bond lengths are 2.72 Å. Sm(1) is bonded in a 6-coordinate geometry to two equivalent Se(1), one O(2), one O(3), and four equivalent O(1) atoms. Both Sm(1)-Se(1) bond lengths are 3.22 Å. The Sm(1)-O(2) bond length is 2.24 Å. The Sm(1)-O(3) bond length is 2.44 Å. There are two shorter (2.46 Å) and two longer (2.59 Å) Sm(1)-O(1) bond lengths. Si(1) is bonded in a tetrahedral geometry to one O(2), one O(3), and two equivalent O(1) atoms. The Si(1)-O(2) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.63 Å. Both Si(1)-O(1) bond lengths are 1.66 Å. Se(1) is bonded to six equivalent Sm(1) atoms to form SeSm6 octahedra that share corners with six equivalent O(3)Ba2SmSi tetrahedra and faces with two equivalent Se(1)Sm6 octahedra. There are three inequivalent O sites. In the first O site, O(3) is bonded to two equivalent Ba(1), one Sm(1), and one Si(1) atom to form distorted OBa2SmSi tetrahedra that share corners with two equivalent Se(1)Sm6 octahedra and edges with two equivalent O(3)Ba2SmSi tetrahedra. The corner-sharing octahedral tilt angles are 81°. In the second O site, O(1) is bonded in a 1-coordinate geometry to one Ba(1), two equivalent Sm(1), and one Si(1) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ba(1), one Sm(1), and one Si(1) atom.