GdNi10Si2 crystallizes in the orthorhombic Immm space group. Gd(1) is bonded in a 20-coordinate geometry to two equivalent Ni(1), two equivalent Ni(2), four equivalent Ni(3), eight equivalent Ni(4), and four equivalent Si(1) atoms. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 14-coordinate geometry to one Gd(1), one Ni(1), two equivalent Ni(3), four equivalent Ni(2), four equivalent Ni(4), and two equivalent Si(1) atoms. In the second Ni site, Ni(2) is bonded in a 14-coordinate geometry to one Gd(1), one Ni(2), two equivalent Ni(3), four equivalent Ni(1), four equivalent Ni(4), and two equivalent Si(1) atoms. In the third Ni site, Ni(3) is bonded in a 12-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), four equivalent Ni(4), and two equivalent Si(1) atoms. In the fourth Ni site, Ni(4) is bonded to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), two equivalent Ni(4), and two equivalent Si(1) atoms to form NiGd2Si2Ni8 cuboctahedra that share corners with four equivalent Si(1)Gd2Ni10 cuboctahedra, corners with ten equivalent Ni(4)Gd2Si2Ni8 cuboctahedra, edges with two equivalent Si(1)Gd2Ni10 cuboctahedra, edges with four equivalent Ni(4)Gd2Si2Ni8 cuboctahedra, faces with four equivalent Si(1)Gd2Ni10 cuboctahedra, and faces with six equivalent Ni(4)Gd2Si2Ni8 cuboctahedra. Si(1) is bonded to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), and four equivalent Ni(4) atoms to form SiGd2Ni10 cuboctahedra that share corners with six equivalent Si(1)Gd2Ni10 cuboctahedra, corners with eight equivalent Ni(4)Gd2Si2Ni8 cuboctahedra, edges with three equivalent Si(1)Gd2Ni10 cuboctahedra, edges with four equivalent Ni(4)Gd2Si2Ni8 cuboctahedra,  a faceface with one Si(1)Gd2Ni10 cuboctahedra, and faces with eight equivalent Ni(4)Gd2Si2Ni8 cuboctahedra.
GdNi10Si2 crystallizes in the orthorhombic Immm space group. Gd(1) is bonded in a 20-coordinate geometry to two equivalent Ni(1), two equivalent Ni(2), four equivalent Ni(3), eight equivalent Ni(4), and four equivalent Si(1) atoms. Both Gd(1)-Ni(1) bond lengths are 2.92 Å. Both Gd(1)-Ni(2) bond lengths are 2.76 Å. All Gd(1)-Ni(3) bond lengths are 2.83 Å. All Gd(1)-Ni(4) bond lengths are 3.09 Å. All Gd(1)-Si(1) bond lengths are 3.12 Å. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 14-coordinate geometry to one Gd(1), one Ni(1), two equivalent Ni(3), four equivalent Ni(2), four equivalent Ni(4), and two equivalent Si(1) atoms. The Ni(1)-Ni(1) bond length is 2.36 Å. Both Ni(1)-Ni(3) bond lengths are 2.69 Å. All Ni(1)-Ni(2) bond lengths are 2.91 Å. All Ni(1)-Ni(4) bond lengths are 2.47 Å. Both Ni(1)-Si(1) bond lengths are 2.53 Å. In the second Ni site, Ni(2) is bonded in a 14-coordinate geometry to one Gd(1), one Ni(2), two equivalent Ni(3), four equivalent Ni(1), four equivalent Ni(4), and two equivalent Si(1) atoms. The Ni(2)-Ni(2) bond length is 2.42 Å. Both Ni(2)-Ni(3) bond lengths are 2.66 Å. All Ni(2)-Ni(4) bond lengths are 2.49 Å. Both Ni(2)-Si(1) bond lengths are 2.40 Å. In the third Ni site, Ni(3) is bonded in a 12-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), four equivalent Ni(4), and two equivalent Si(1) atoms. All Ni(3)-Ni(4) bond lengths are 2.41 Å. Both Ni(3)-Si(1) bond lengths are 2.56 Å. In the fourth Ni site, Ni(4) is bonded to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), two equivalent Ni(4), and two equivalent Si(1) atoms to form NiGd2Si2Ni8 cuboctahedra that share corners with four equivalent Si(1)Gd2Ni10 cuboctahedra, corners with ten equivalent Ni(4)Gd2Si2Ni8 cuboctahedra, edges with two equivalent Si(1)Gd2Ni10 cuboctahedra, edges with four equivalent Ni(4)Gd2Si2Ni8 cuboctahedra, faces with four equivalent Si(1)Gd2Ni10 cuboctahedra, and faces with six equivalent Ni(4)Gd2Si2Ni8 cuboctahedra. Both Ni(4)-Ni(4) bond lengths are 2.37 Å. Both Ni(4)-Si(1) bond lengths are 2.31 Å. Si(1) is bonded to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), and four equivalent Ni(4) atoms to form SiGd2Ni10 cuboctahedra that share corners with six equivalent Si(1)Gd2Ni10 cuboctahedra, corners with eight equivalent Ni(4)Gd2Si2Ni8 cuboctahedra, edges with three equivalent Si(1)Gd2Ni10 cuboctahedra, edges with four equivalent Ni(4)Gd2Si2Ni8 cuboctahedra,  a faceface with one Si(1)Gd2Ni10 cuboctahedra, and faces with eight equivalent Ni(4)Gd2Si2Ni8 cuboctahedra.