Sm2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), two equivalent O(6), and two equivalent O(7) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form corner-sharing SiO4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Sm(1), one Si(1), and one Si(2) atom. In the second O site, O(6) is bonded to one Sm(1), two equivalent Sm(2), and one Si(2) atom to form distorted edge-sharing OSm3Si tetrahedra. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Sm(1), two equivalent Sm(2), and one Si(1) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Sm(1), one Sm(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a 1-coordinate geometry to one Sm(1), one Sm(2), and one Si(2) atom. In the sixth O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Sm(1), one Sm(2), and one Si(2) atom. In the seventh O site, O(4) is bonded in a distorted single-bond geometry to one Sm(1), one Sm(2), and one Si(1) atom.
Sm2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Sm sites. In the first Sm site, Sm(1) is bonded in a 7-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom. The Sm(1)-O(1) bond length is 2.45 Å. The Sm(1)-O(2) bond length is 2.37 Å. The Sm(1)-O(3) bond length is 2.41 Å. The Sm(1)-O(4) bond length is 2.49 Å. The Sm(1)-O(5) bond length is 2.61 Å. The Sm(1)-O(6) bond length is 2.49 Å. The Sm(1)-O(7) bond length is 2.42 Å. In the second Sm site, Sm(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(4), two equivalent O(6), and two equivalent O(7) atoms. The Sm(2)-O(1) bond length is 2.32 Å. The Sm(2)-O(2) bond length is 2.56 Å. The Sm(2)-O(3) bond length is 2.41 Å. The Sm(2)-O(4) bond length is 2.49 Å. There is one shorter (2.43 Å) and one longer (2.45 Å) Sm(2)-O(6) bond length. There is one shorter (2.55 Å) and one longer (2.65 Å) Sm(2)-O(7) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(5), and one O(7) atom to form corner-sharing SiO4 tetrahedra. The Si(1)-O(1) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.68 Å. The Si(1)-O(7) bond length is 1.65 Å. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(5), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(2) bond length is 1.63 Å. The Si(2)-O(3) bond length is 1.62 Å. The Si(2)-O(5) bond length is 1.67 Å. The Si(2)-O(6) bond length is 1.66 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Sm(1), one Si(1), and one Si(2) atom. In the second O site, O(6) is bonded to one Sm(1), two equivalent Sm(2), and one Si(2) atom to form distorted edge-sharing OSm3Si tetrahedra. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Sm(1), two equivalent Sm(2), and one Si(1) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Sm(1), one Sm(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a 1-coordinate geometry to one Sm(1), one Sm(2), and one Si(2) atom. In the sixth O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Sm(1), one Sm(2), and one Si(2) atom. In the seventh O site, O(4) is bonded in a distorted single-bond geometry to one Sm(1), one Sm(2), and one Si(1) atom.