Ce10Si8O3 crystallizes in the hexagonal P6/mmm space group. There are three inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Si(1), four equivalent Si(2), and two equivalent O(1) atoms. In the second Ce site, Ce(2) is bonded in a distorted linear geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent O(1) atoms. In the third Ce site, Ce(3) is bonded to twelve equivalent Si(2) atoms to form face-sharing CeSi12 cuboctahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Ce(2) and six equivalent Ce(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Ce(2), two equivalent Ce(3), four equivalent Ce(1), and two equivalent Si(2) atoms. O(1) is bonded to two equivalent Ce(2) and four equivalent Ce(1) atoms to form corner-sharing OCe6 octahedra. The corner-sharing octahedral tilt angles range from 0-31°.
Ce10Si8O3 crystallizes in the hexagonal P6/mmm space group. There are three inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a distorted bent 150 degrees geometry to two equivalent Si(1), four equivalent Si(2), and two equivalent O(1) atoms. Both Ce(1)-Si(1) bond lengths are 3.23 Å. All Ce(1)-Si(2) bond lengths are 3.18 Å. Both Ce(1)-O(1) bond lengths are 2.80 Å. In the second Ce site, Ce(2) is bonded in a distorted linear geometry to two equivalent Si(1), two equivalent Si(2), and two equivalent O(1) atoms. Both Ce(2)-Si(1) bond lengths are 3.12 Å. Both Ce(2)-Si(2) bond lengths are 3.03 Å. Both Ce(2)-O(1) bond lengths are 2.27 Å. In the third Ce site, Ce(3) is bonded to twelve equivalent Si(2) atoms to form face-sharing CeSi12 cuboctahedra. All Ce(3)-Si(2) bond lengths are 3.29 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Ce(2) and six equivalent Ce(1) atoms. In the second Si site, Si(2) is bonded in a 9-coordinate geometry to one Ce(2), two equivalent Ce(3), four equivalent Ce(1), and two equivalent Si(2) atoms. Both Si(2)-Si(2) bond lengths are 2.37 Å. O(1) is bonded to two equivalent Ce(2) and four equivalent Ce(1) atoms to form corner-sharing OCe6 octahedra. The corner-sharing octahedral tilt angles range from 0-31°.