Tb4SiBr6 is trigonal omega-derived structured and crystallizes in the orthorhombic Pbam space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one Si(1), one Br(1), two equivalent Br(2), and two equivalent Br(3) atoms to form TbSiBr5 octahedra that share  a cornercorner with one Tb(1)SiBr5 octahedra, corners with two equivalent Tb(2)Si2Br4 octahedra, edges with two equivalent Tb(1)SiBr5 octahedra, and edges with four equivalent Tb(2)Si2Br4 octahedra. The corner-sharing octahedral tilt angles range from 0-48°. In the second Tb site, Tb(2) is bonded to two equivalent Si(1), one Br(2), one Br(3), and two equivalent Br(1) atoms to form TbSi2Br4 octahedra that share corners with two equivalent Tb(2)Si2Br4 octahedra, corners with two equivalent Tb(1)SiBr5 octahedra, edges with three equivalent Tb(2)Si2Br4 octahedra, and edges with four equivalent Tb(1)SiBr5 octahedra. The corner-sharing octahedral tilt angles range from 0-48°. Si(1) is bonded to two equivalent Tb(1) and four equivalent Tb(2) atoms to form edge-sharing SiTb6 octahedra. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded in a distorted T-shaped geometry to one Tb(1) and two equivalent Tb(2) atoms. In the second Br site, Br(2) is bonded in a distorted T-shaped geometry to one Tb(2) and two equivalent Tb(1) atoms. In the third Br site, Br(3) is bonded in a distorted T-shaped geometry to one Tb(2) and two equivalent Tb(1) atoms.
Tb4SiBr6 is trigonal omega-derived structured and crystallizes in the orthorhombic Pbam space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one Si(1), one Br(1), two equivalent Br(2), and two equivalent Br(3) atoms to form TbSiBr5 octahedra that share  a cornercorner with one Tb(1)SiBr5 octahedra, corners with two equivalent Tb(2)Si2Br4 octahedra, edges with two equivalent Tb(1)SiBr5 octahedra, and edges with four equivalent Tb(2)Si2Br4 octahedra. The corner-sharing octahedral tilt angles range from 0-48°. The Tb(1)-Si(1) bond length is 2.72 Å. The Tb(1)-Br(1) bond length is 2.99 Å. Both Tb(1)-Br(2) bond lengths are 2.89 Å. Both Tb(1)-Br(3) bond lengths are 2.89 Å. In the second Tb site, Tb(2) is bonded to two equivalent Si(1), one Br(2), one Br(3), and two equivalent Br(1) atoms to form TbSi2Br4 octahedra that share corners with two equivalent Tb(2)Si2Br4 octahedra, corners with two equivalent Tb(1)SiBr5 octahedra, edges with three equivalent Tb(2)Si2Br4 octahedra, and edges with four equivalent Tb(1)SiBr5 octahedra. The corner-sharing octahedral tilt angles range from 0-48°. Both Tb(2)-Si(1) bond lengths are 2.79 Å. The Tb(2)-Br(2) bond length is 2.96 Å. The Tb(2)-Br(3) bond length is 2.97 Å. Both Tb(2)-Br(1) bond lengths are 2.97 Å. Si(1) is bonded to two equivalent Tb(1) and four equivalent Tb(2) atoms to form edge-sharing SiTb6 octahedra. There are three inequivalent Br sites. In the first Br site, Br(1) is bonded in a distorted T-shaped geometry to one Tb(1) and two equivalent Tb(2) atoms. In the second Br site, Br(2) is bonded in a distorted T-shaped geometry to one Tb(2) and two equivalent Tb(1) atoms. In the third Br site, Br(3) is bonded in a distorted T-shaped geometry to one Tb(2) and two equivalent Tb(1) atoms.