Ni5Ga21 crystallizes in the orthorhombic Fmm2 space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 11-coordinate geometry to one Ga(4), one Ga(5), one Ga(6), one Ga(7), one Ga(8), three equivalent Ga(1), and three equivalent Ga(3) atoms. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to one Ga(9), two equivalent Ga(2), two equivalent Ga(4), two equivalent Ga(6), and two equivalent Ga(7) atoms. There are nine inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 1-coordinate geometry to three equivalent Ni(1), one Ga(2), one Ga(4), one Ga(5), and one Ga(8) atom. In the second Ga site, Ga(2) is bonded in a 9-coordinate geometry to one Ni(2), one Ga(5), one Ga(9), two equivalent Ga(1), two equivalent Ga(3), and two equivalent Ga(7) atoms. In the third Ga site, Ga(3) is bonded in a 1-coordinate geometry to three equivalent Ni(1), one Ga(2), one Ga(4), one Ga(6), and one Ga(7) atom. In the fourth Ga site, Ga(4) is bonded in a 11-coordinate geometry to one Ni(2), two equivalent Ni(1), one Ga(6), one Ga(9), two equivalent Ga(1), two equivalent Ga(3), and two equivalent Ga(8) atoms. In the fifth Ga site, Ga(5) is bonded in a 9-coordinate geometry to two equivalent Ni(1), one Ga(2), one Ga(7), one Ga(9), two equivalent Ga(1), and two equivalent Ga(8) atoms. In the sixth Ga site, Ga(6) is bonded in a 9-coordinate geometry to one Ni(2), two equivalent Ni(1), one Ga(4), one Ga(8), two equivalent Ga(3), and two equivalent Ga(7) atoms. In the seventh Ga site, Ga(7) is bonded in a 10-coordinate geometry to one Ni(2), two equivalent Ni(1), one Ga(5), two equivalent Ga(2), two equivalent Ga(3), and two equivalent Ga(6) atoms. In the eighth Ga site, Ga(8) is bonded in a 10-coordinate geometry to two equivalent Ni(1), one Ga(6), one Ga(9), two equivalent Ga(1), two equivalent Ga(4), and two equivalent Ga(5) atoms. In the ninth Ga site, Ga(9) is bonded in a 9-coordinate geometry to one Ni(2), two equivalent Ga(2), two equivalent Ga(4), two equivalent Ga(5), and two equivalent Ga(8) atoms.
Ni5Ga21 crystallizes in the orthorhombic Fmm2 space group. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a 11-coordinate geometry to one Ga(4), one Ga(5), one Ga(6), one Ga(7), one Ga(8), three equivalent Ga(1), and three equivalent Ga(3) atoms. The Ni(1)-Ga(4) bond length is 3.10 Å. The Ni(1)-Ga(5) bond length is 2.65 Å. The Ni(1)-Ga(6) bond length is 2.64 Å. The Ni(1)-Ga(7) bond length is 2.71 Å. The Ni(1)-Ga(8) bond length is 2.63 Å. There are a spread of Ni(1)-Ga(1) bond distances ranging from 2.58-2.90 Å. There are a spread of Ni(1)-Ga(3) bond distances ranging from 2.55-2.92 Å. In the second Ni site, Ni(2) is bonded in a 9-coordinate geometry to one Ga(9), two equivalent Ga(2), two equivalent Ga(4), two equivalent Ga(6), and two equivalent Ga(7) atoms. The Ni(2)-Ga(9) bond length is 2.52 Å. Both Ni(2)-Ga(2) bond lengths are 2.61 Å. Both Ni(2)-Ga(4) bond lengths are 3.00 Å. Both Ni(2)-Ga(6) bond lengths are 2.43 Å. Both Ni(2)-Ga(7) bond lengths are 2.72 Å. There are nine inequivalent Ga sites. In the first Ga site, Ga(1) is bonded in a 1-coordinate geometry to three equivalent Ni(1), one Ga(2), one Ga(4), one Ga(5), and one Ga(8) atom. The Ga(1)-Ga(2) bond length is 2.77 Å. The Ga(1)-Ga(4) bond length is 2.84 Å. The Ga(1)-Ga(5) bond length is 2.85 Å. The Ga(1)-Ga(8) bond length is 2.98 Å. In the second Ga site, Ga(2) is bonded in a 9-coordinate geometry to one Ni(2), one Ga(5), one Ga(9), two equivalent Ga(1), two equivalent Ga(3), and two equivalent Ga(7) atoms. The Ga(2)-Ga(5) bond length is 2.87 Å. The Ga(2)-Ga(9) bond length is 2.74 Å. Both Ga(2)-Ga(3) bond lengths are 2.81 Å. There is one shorter (2.68 Å) and one longer (2.87 Å) Ga(2)-Ga(7) bond length. In the third Ga site, Ga(3) is bonded in a 1-coordinate geometry to three equivalent Ni(1), one Ga(2), one Ga(4), one Ga(6), and one Ga(7) atom. The Ga(3)-Ga(4) bond length is 2.73 Å. The Ga(3)-Ga(6) bond length is 2.86 Å. The Ga(3)-Ga(7) bond length is 2.97 Å. In the fourth Ga site, Ga(4) is bonded in a 11-coordinate geometry to one Ni(2), two equivalent Ni(1), one Ga(6), one Ga(9), two equivalent Ga(1), two equivalent Ga(3), and two equivalent Ga(8) atoms. The Ga(4)-Ga(6) bond length is 2.88 Å. The Ga(4)-Ga(9) bond length is 2.75 Å. There is one shorter (2.72 Å) and one longer (2.74 Å) Ga(4)-Ga(8) bond length. In the fifth Ga site, Ga(5) is bonded in a 9-coordinate geometry to two equivalent Ni(1), one Ga(2), one Ga(7), one Ga(9), two equivalent Ga(1), and two equivalent Ga(8) atoms. The Ga(5)-Ga(7) bond length is 2.66 Å. The Ga(5)-Ga(9) bond length is 2.68 Å. Both Ga(5)-Ga(8) bond lengths are 2.95 Å. In the sixth Ga site, Ga(6) is bonded in a 9-coordinate geometry to one Ni(2), two equivalent Ni(1), one Ga(4), one Ga(8), two equivalent Ga(3), and two equivalent Ga(7) atoms. The Ga(6)-Ga(8) bond length is 2.69 Å. Both Ga(6)-Ga(7) bond lengths are 2.86 Å. In the seventh Ga site, Ga(7) is bonded in a 10-coordinate geometry to one Ni(2), two equivalent Ni(1), one Ga(5), two equivalent Ga(2), two equivalent Ga(3), and two equivalent Ga(6) atoms. In the eighth Ga site, Ga(8) is bonded in a 10-coordinate geometry to two equivalent Ni(1), one Ga(6), one Ga(9), two equivalent Ga(1), two equivalent Ga(4), and two equivalent Ga(5) atoms. The Ga(8)-Ga(9) bond length is 2.82 Å. In the ninth Ga site, Ga(9) is bonded in a 9-coordinate geometry to one Ni(2), two equivalent Ga(2), two equivalent Ga(4), two equivalent Ga(5), and two equivalent Ga(8) atoms.