Gd2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Gd sites. In the first Gd site, Gd(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 Gd site, Gd(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 Gd(1), one Si(1), and one Si(2) atom. In the second O site, O(6) is bonded to one Gd(1), two equivalent Gd(2), and one Si(2) atom to form distorted edge-sharing OGd3Si tetrahedra. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Gd(1), two equivalent Gd(2), and one Si(1) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Gd(1), one Gd(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Gd(1), one Gd(2), and one Si(2) atom. In the sixth O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Gd(1), one Gd(2), and one Si(2) atom. In the seventh O site, O(4) is bonded in a distorted single-bond geometry to one Gd(1), one Gd(2), and one Si(1) atom.
Gd2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Gd sites. In the first Gd site, Gd(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 Gd(1)-O(1) bond length is 2.42 Å. The Gd(1)-O(2) bond length is 2.32 Å. The Gd(1)-O(3) bond length is 2.39 Å. The Gd(1)-O(4) bond length is 2.46 Å. The Gd(1)-O(5) bond length is 2.60 Å. The Gd(1)-O(6) bond length is 2.48 Å. The Gd(1)-O(7) bond length is 2.39 Å. In the second Gd site, Gd(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 Gd(2)-O(1) bond length is 2.29 Å. The Gd(2)-O(2) bond length is 2.51 Å. The Gd(2)-O(3) bond length is 2.39 Å. The Gd(2)-O(4) bond length is 2.49 Å. There is one shorter (2.42 Å) and one longer (2.43 Å) Gd(2)-O(6) bond length. There is one shorter (2.54 Å) and one longer (2.64 Å) Gd(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 1.63 Å. The Si(1)-O(5) bond length is 1.67 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 1.68 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 Gd(1), one Si(1), and one Si(2) atom. In the second O site, O(6) is bonded to one Gd(1), two equivalent Gd(2), and one Si(2) atom to form distorted edge-sharing OGd3Si tetrahedra. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Gd(1), two equivalent Gd(2), and one Si(1) atom. In the fourth O site, O(1) is bonded in a distorted trigonal planar geometry to one Gd(1), one Gd(2), and one Si(1) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Gd(1), one Gd(2), and one Si(2) atom. In the sixth O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Gd(1), one Gd(2), and one Si(2) atom. In the seventh O site, O(4) is bonded in a distorted single-bond geometry to one Gd(1), one Gd(2), and one Si(1) atom.