Th2PtSi3 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Th sites. In the first Th site, Th(1) is bonded to four equivalent Pt(1), two equivalent Si(1), two equivalent Si(3), and four equivalent Si(2) atoms to form ThSi8Pt4 cuboctahedra that share edges with four equivalent Th(1)Si8Pt4 cuboctahedra, edges with eight equivalent Th(2)Si10Pt2 cuboctahedra, faces with four equivalent Th(2)Si10Pt2 cuboctahedra, and faces with four equivalent Th(1)Si8Pt4 cuboctahedra. In the second Th site, Th(2) is bonded to two equivalent Pt(1), two equivalent Si(2), four equivalent Si(1), and four equivalent Si(3) atoms to form ThSi10Pt2 cuboctahedra that share edges with four equivalent Th(2)Si10Pt2 cuboctahedra, edges with eight equivalent Th(1)Si8Pt4 cuboctahedra, faces with four equivalent Th(2)Si10Pt2 cuboctahedra, and faces with four equivalent Th(1)Si8Pt4 cuboctahedra. Pt(1) is bonded in a 9-coordinate geometry to two equivalent Th(2), four equivalent Th(1), one Si(2), and two equivalent Si(1) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Th(1), four equivalent Th(2), two equivalent Pt(1), and one Si(3) atom. In the second Si site, Si(2) is bonded in a distorted single-bond geometry to two equivalent Th(2), four equivalent Th(1), one Pt(1), and two equivalent Si(3) atoms. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Th(1), four equivalent Th(2), one Si(1), and two equivalent Si(2) atoms.
Th2PtSi3 crystallizes in the orthorhombic Imm2 space group. There are two inequivalent Th sites. In the first Th site, Th(1) is bonded to four equivalent Pt(1), two equivalent Si(1), two equivalent Si(3), and four equivalent Si(2) atoms to form ThSi8Pt4 cuboctahedra that share edges with four equivalent Th(1)Si8Pt4 cuboctahedra, edges with eight equivalent Th(2)Si10Pt2 cuboctahedra, faces with four equivalent Th(2)Si10Pt2 cuboctahedra, and faces with four equivalent Th(1)Si8Pt4 cuboctahedra. All Th(1)-Pt(1) bond lengths are 3.24 Å. Both Th(1)-Si(1) bond lengths are 3.21 Å. Both Th(1)-Si(3) bond lengths are 3.09 Å. All Th(1)-Si(2) bond lengths are 3.19 Å. In the second Th site, Th(2) is bonded to two equivalent Pt(1), two equivalent Si(2), four equivalent Si(1), and four equivalent Si(3) atoms to form ThSi10Pt2 cuboctahedra that share edges with four equivalent Th(2)Si10Pt2 cuboctahedra, edges with eight equivalent Th(1)Si8Pt4 cuboctahedra, faces with four equivalent Th(2)Si10Pt2 cuboctahedra, and faces with four equivalent Th(1)Si8Pt4 cuboctahedra. Both Th(2)-Pt(1) bond lengths are 3.16 Å. Both Th(2)-Si(2) bond lengths are 3.14 Å. All Th(2)-Si(1) bond lengths are 3.21 Å. All Th(2)-Si(3) bond lengths are 3.21 Å. Pt(1) is bonded in a 9-coordinate geometry to two equivalent Th(2), four equivalent Th(1), one Si(2), and two equivalent Si(1) atoms. The Pt(1)-Si(2) bond length is 2.37 Å. Both Pt(1)-Si(1) bond lengths are 2.40 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to two equivalent Th(1), four equivalent Th(2), two equivalent Pt(1), and one Si(3) atom. The Si(1)-Si(3) bond length is 2.37 Å. In the second Si site, Si(2) is bonded in a distorted single-bond geometry to two equivalent Th(2), four equivalent Th(1), one Pt(1), and two equivalent Si(3) atoms. Both Si(2)-Si(3) bond lengths are 2.41 Å. In the third Si site, Si(3) is bonded in a 9-coordinate geometry to two equivalent Th(1), four equivalent Th(2), one Si(1), and two equivalent Si(2) atoms.