Tb5Si3O13 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), and four equivalent O(2) atoms. In the second Tb site, Tb(2) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. Si(1) is bonded in a tetrahedral geometry to one O(1), one O(3), and two equivalent O(2) atoms. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Tb(1), two equivalent Tb(2), and one Si(1) atom to form distorted edge-sharing OTb3Si tetrahedra. In the second O site, O(4) is bonded in a trigonal planar geometry to three equivalent Tb(1) atoms. In the third O site, O(1) is bonded in a 4-coordinate geometry to one Tb(1), two equivalent Tb(2), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Tb(2), two equivalent Tb(1), and one Si(1) atom.
Tb5Si3O13 crystallizes in the hexagonal P6_3/m space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded in a 7-coordinate geometry to one O(1), one O(3), one O(4), and four equivalent O(2) atoms. The Tb(1)-O(1) bond length is 2.78 Å. The Tb(1)-O(3) bond length is 2.45 Å. The Tb(1)-O(4) bond length is 2.22 Å. There are two shorter (2.31 Å) and two longer (2.44 Å) Tb(1)-O(2) bond lengths. In the second Tb site, Tb(2) is bonded in a 9-coordinate geometry to three equivalent O(1), three equivalent O(2), and three equivalent O(3) atoms. All Tb(2)-O(1) bond lengths are 2.34 Å. All Tb(2)-O(2) bond lengths are 2.85 Å. All Tb(2)-O(3) bond lengths are 2.44 Å. Si(1) is bonded in a tetrahedral geometry to one O(1), one O(3), and two equivalent O(2) atoms. The Si(1)-O(1) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.65 Å. Both Si(1)-O(2) bond lengths are 1.65 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Tb(1), two equivalent Tb(2), and one Si(1) atom to form distorted edge-sharing OTb3Si tetrahedra. In the second O site, O(4) is bonded in a trigonal planar geometry to three equivalent Tb(1) atoms. In the third O site, O(1) is bonded in a 4-coordinate geometry to one Tb(1), two equivalent Tb(2), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 3-coordinate geometry to one Tb(2), two equivalent Tb(1), and one Si(1) atom.