Gd3CuSiSe7 crystallizes in the hexagonal P6_3 space group. Gd(1) is bonded in a 8-coordinate geometry to one Se(2), three equivalent Se(1), and four equivalent Se(3) atoms. Cu(1) is bonded in a trigonal planar geometry to three equivalent Se(3) atoms. Si(1) is bonded in a tetrahedral geometry to one Se(2) and three equivalent Se(1) atoms. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Gd(1) and one Si(1) atom. In the second Se site, Se(2) is bonded in a distorted tetrahedral geometry to three equivalent Gd(1) and one Si(1) atom. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to four equivalent Gd(1) and one Cu(1) atom.
Gd3CuSiSe7 crystallizes in the hexagonal P6_3 space group. Gd(1) is bonded in a 8-coordinate geometry to one Se(2), three equivalent Se(1), and four equivalent Se(3) atoms. The Gd(1)-Se(2) bond length is 3.13 Å. There are a spread of Gd(1)-Se(1) bond distances ranging from 2.94-3.16 Å. There are a spread of Gd(1)-Se(3) bond distances ranging from 2.90-3.25 Å. Cu(1) is bonded in a trigonal planar geometry to three equivalent Se(3) atoms. All Cu(1)-Se(3) bond lengths are 2.35 Å. Si(1) is bonded in a tetrahedral geometry to one Se(2) and three equivalent Se(1) atoms. The Si(1)-Se(2) bond length is 2.25 Å. All Si(1)-Se(1) bond lengths are 2.28 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted rectangular see-saw-like geometry to three equivalent Gd(1) and one Si(1) atom. In the second Se site, Se(2) is bonded in a distorted tetrahedral geometry to three equivalent Gd(1) and one Si(1) atom. In the third Se site, Se(3) is bonded in a 5-coordinate geometry to four equivalent Gd(1) and one Cu(1) atom.