GdNiSi2 crystallizes in the orthorhombic Cmcm space group. Gd(1) is bonded in a 14-coordinate geometry to four equivalent Ni(1), four equivalent Si(2), and six equivalent Si(1) atoms. Ni(1) is bonded in a 9-coordinate geometry to four equivalent Gd(1), one Si(1), and four equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent Gd(1), one Ni(1), and two equivalent Si(1) atoms. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to four equivalent Gd(1) and four equivalent Ni(1) atoms.
GdNiSi2 crystallizes in the orthorhombic Cmcm space group. Gd(1) is bonded in a 14-coordinate geometry to four equivalent Ni(1), four equivalent Si(2), and six equivalent Si(1) atoms. All Gd(1)-Ni(1) bond lengths are 3.07 Å. There are two shorter (3.07 Å) and two longer (3.10 Å) Gd(1)-Si(2) bond lengths. There are four shorter (3.03 Å) and two longer (3.14 Å) Gd(1)-Si(1) bond lengths. Ni(1) is bonded in a 9-coordinate geometry to four equivalent Gd(1), one Si(1), and four equivalent Si(2) atoms. The Ni(1)-Si(1) bond length is 2.26 Å. There are two shorter (2.30 Å) and two longer (2.32 Å) Ni(1)-Si(2) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to six equivalent Gd(1), one Ni(1), and two equivalent Si(1) atoms. Both Si(1)-Si(1) bond lengths are 2.39 Å. In the second Si site, Si(2) is bonded in a 8-coordinate geometry to four equivalent Gd(1) and four equivalent Ni(1) atoms.