GdNi8Si3 crystallizes in the monoclinic C2/c space group. Gd(1) is bonded in a 22-coordinate geometry to two equivalent Ni(4), two equivalent Ni(5), four equivalent Ni(1), four equivalent Ni(2), four equivalent Ni(3), two equivalent Si(2), and four equivalent Si(1) atoms. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(1), one Ni(3), one Ni(4), one Ni(5), three equivalent Ni(2), one Si(2), and two equivalent Si(1) atoms. In the second Ni site, Ni(2) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(2), one Ni(4), two equivalent Ni(3), three equivalent Ni(1), one Si(1), and two equivalent Si(2) atoms. In the third Ni site, Ni(3) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(1), one Ni(3), one Ni(4), one Ni(5), two equivalent Ni(2), one Si(2), and three equivalent Si(1) atoms. In the fourth Ni site, Ni(4) is bonded in a 14-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), two equivalent Ni(5), two equivalent Si(1), and two equivalent Si(2) atoms. In the fifth Ni site, Ni(5) is bonded in a 10-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(3), two equivalent Ni(4), and four equivalent Si(1) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(2), one Ni(4), two equivalent Ni(1), two equivalent Ni(5), three equivalent Ni(3), and one Si(1) atom. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(3), two equivalent Ni(4), and four equivalent Ni(2) atoms.
GdNi8Si3 crystallizes in the monoclinic C2/c space group. Gd(1) is bonded in a 22-coordinate geometry to two equivalent Ni(4), two equivalent Ni(5), four equivalent Ni(1), four equivalent Ni(2), four equivalent Ni(3), two equivalent Si(2), and four equivalent Si(1) atoms. Both Gd(1)-Ni(4) bond lengths are 3.13 Å. Both Gd(1)-Ni(5) bond lengths are 3.43 Å. There are two shorter (2.97 Å) and two longer (3.02 Å) Gd(1)-Ni(1) bond lengths. There are two shorter (3.00 Å) and two longer (3.07 Å) Gd(1)-Ni(2) bond lengths. There are two shorter (2.93 Å) and two longer (3.09 Å) Gd(1)-Ni(3) bond lengths. Both Gd(1)-Si(2) bond lengths are 3.29 Å. There are two shorter (3.13 Å) and two longer (3.15 Å) Gd(1)-Si(1) bond lengths. There are five inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(1), one Ni(3), one Ni(4), one Ni(5), three equivalent Ni(2), one Si(2), and two equivalent Si(1) atoms. The Ni(1)-Ni(1) bond length is 2.42 Å. The Ni(1)-Ni(3) bond length is 2.78 Å. The Ni(1)-Ni(4) bond length is 2.60 Å. The Ni(1)-Ni(5) bond length is 2.38 Å. There are a spread of Ni(1)-Ni(2) bond distances ranging from 2.38-2.49 Å. The Ni(1)-Si(2) bond length is 2.33 Å. There is one shorter (2.35 Å) and one longer (2.51 Å) Ni(1)-Si(1) bond length. In the second Ni site, Ni(2) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(2), one Ni(4), two equivalent Ni(3), three equivalent Ni(1), one Si(1), and two equivalent Si(2) atoms. The Ni(2)-Ni(2) bond length is 2.48 Å. The Ni(2)-Ni(4) bond length is 2.60 Å. There is one shorter (2.42 Å) and one longer (2.65 Å) Ni(2)-Ni(3) bond length. The Ni(2)-Si(1) bond length is 2.35 Å. Both Ni(2)-Si(2) bond lengths are 2.33 Å. In the third Ni site, Ni(3) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(1), one Ni(3), one Ni(4), one Ni(5), two equivalent Ni(2), one Si(2), and three equivalent Si(1) atoms. The Ni(3)-Ni(3) bond length is 2.53 Å. The Ni(3)-Ni(4) bond length is 2.62 Å. The Ni(3)-Ni(5) bond length is 2.35 Å. The Ni(3)-Si(2) bond length is 2.47 Å. There are a spread of Ni(3)-Si(1) bond distances ranging from 2.35-2.39 Å. In the fourth Ni site, Ni(4) is bonded in a 14-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(2), two equivalent Ni(3), two equivalent Ni(5), two equivalent Si(1), and two equivalent Si(2) atoms. Both Ni(4)-Ni(5) bond lengths are 2.49 Å. Both Ni(4)-Si(1) bond lengths are 2.64 Å. Both Ni(4)-Si(2) bond lengths are 2.56 Å. In the fifth Ni site, Ni(5) is bonded in a 10-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(3), two equivalent Ni(4), and four equivalent Si(1) atoms. There are two shorter (2.35 Å) and two longer (2.38 Å) Ni(5)-Si(1) bond lengths. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 12-coordinate geometry to two equivalent Gd(1), one Ni(2), one Ni(4), two equivalent Ni(1), two equivalent Ni(5), three equivalent Ni(3), and one Si(1) atom. The Si(1)-Si(1) bond length is 2.64 Å. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Gd(1), two equivalent Ni(1), two equivalent Ni(3), two equivalent Ni(4), and four equivalent Ni(2) atoms.