Ni31Si12 crystallizes in the trigonal P321 space group. There are eight inequivalent Ni sites. In the first Ni site, Ni(5) is bonded in a 13-coordinate geometry to three equivalent Ni(3), six equivalent Ni(4), one Si(3), and three equivalent Si(1) atoms. In the second Ni site, Ni(6) is bonded in a 13-coordinate geometry to three equivalent Ni(2), six equivalent Ni(1), one Si(4), and three equivalent Si(2) atoms. In the third Ni site, Ni(7) is bonded in a 11-coordinate geometry to one Ni(7), three equivalent Ni(1), three equivalent Ni(2), one Si(5), and three equivalent Si(2) atoms. In the fourth Ni site, Ni(8) is bonded in a 11-coordinate geometry to six equivalent Ni(4), two equivalent Si(5), and three equivalent Si(1) atoms. In the fifth Ni site, Ni(1) is bonded in a 14-coordinate geometry to one Ni(3), one Ni(7), two equivalent Ni(6), three equivalent Ni(1), three equivalent Ni(2), one Si(3), and three equivalent Si(2) atoms. In the sixth Ni site, Ni(2) is bonded in a 13-coordinate geometry to one Ni(4), one Ni(6), one Ni(7), three equivalent Ni(1), three equivalent Ni(3), one Si(2), one Si(3), one Si(4), and one Si(5) atom. In the seventh Ni site, Ni(3) is bonded in a 12-coordinate geometry to one Ni(1), one Ni(5), three equivalent Ni(2), three equivalent Ni(4), one Si(1), one Si(3), one Si(4), and one Si(5) atom. In the eighth Ni site, Ni(4) is bonded in a 13-coordinate geometry to one Ni(2), one Ni(4), one Ni(8), two equivalent Ni(5), three equivalent Ni(3), one Si(4), one Si(5), and three equivalent Si(1) atoms. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Ni(8), two equivalent Ni(3), two equivalent Ni(5), and six equivalent Ni(4) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Ni(2), two equivalent Ni(6), two equivalent Ni(7), and six equivalent Ni(1) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Ni(5), three equivalent Ni(1), three equivalent Ni(2), and three equivalent Ni(3) atoms. In the fourth Si site, Si(4) is bonded in a distorted q6 geometry to one Ni(6), three equivalent Ni(2), three equivalent Ni(3), and three equivalent Ni(4) atoms. In the fifth Si site, Si(5) is bonded in a 11-coordinate geometry to one Ni(7), one Ni(8), three equivalent Ni(2), three equivalent Ni(3), and three equivalent Ni(4) atoms.
Ni31Si12 crystallizes in the trigonal P321 space group. There are eight inequivalent Ni sites. In the first Ni site, Ni(5) is bonded in a 13-coordinate geometry to three equivalent Ni(3), six equivalent Ni(4), one Si(3), and three equivalent Si(1) atoms. All Ni(5)-Ni(3) bond lengths are 2.54 Å. There are three shorter (2.51 Å) and three longer (2.74 Å) Ni(5)-Ni(4) bond lengths. The Ni(5)-Si(3) bond length is 2.51 Å. All Ni(5)-Si(1) bond lengths are 2.29 Å. In the second Ni site, Ni(6) is bonded in a 13-coordinate geometry to three equivalent Ni(2), six equivalent Ni(1), one Si(4), and three equivalent Si(2) atoms. All Ni(6)-Ni(2) bond lengths are 2.58 Å. There are three shorter (2.51 Å) and three longer (2.65 Å) Ni(6)-Ni(1) bond lengths. The Ni(6)-Si(4) bond length is 2.46 Å. All Ni(6)-Si(2) bond lengths are 2.42 Å. In the third Ni site, Ni(7) is bonded in a 11-coordinate geometry to one Ni(7), three equivalent Ni(1), three equivalent Ni(2), one Si(5), and three equivalent Si(2) atoms. The Ni(7)-Ni(7) bond length is 2.36 Å. All Ni(7)-Ni(1) bond lengths are 2.50 Å. All Ni(7)-Ni(2) bond lengths are 2.43 Å. The Ni(7)-Si(5) bond length is 2.38 Å. All Ni(7)-Si(2) bond lengths are 2.41 Å. In the fourth Ni site, Ni(8) is bonded in a 11-coordinate geometry to six equivalent Ni(4), two equivalent Si(5), and three equivalent Si(1) atoms. All Ni(8)-Ni(4) bond lengths are 2.54 Å. Both Ni(8)-Si(5) bond lengths are 2.51 Å. All Ni(8)-Si(1) bond lengths are 2.31 Å. In the fifth Ni site, Ni(1) is bonded in a 14-coordinate geometry to one Ni(3), one Ni(7), two equivalent Ni(6), three equivalent Ni(1), three equivalent Ni(2), one Si(3), and three equivalent Si(2) atoms. The Ni(1)-Ni(3) bond length is 2.57 Å. There is one shorter (2.48 Å) and two longer (2.91 Å) Ni(1)-Ni(1) bond lengths. There are a spread of Ni(1)-Ni(2) bond distances ranging from 2.49-2.77 Å. The Ni(1)-Si(3) bond length is 2.32 Å. There are a spread of Ni(1)-Si(2) bond distances ranging from 2.28-2.91 Å. In the sixth Ni site, Ni(2) is bonded in a 13-coordinate geometry to one Ni(4), one Ni(6), one Ni(7), three equivalent Ni(1), three equivalent Ni(3), one Si(2), one Si(3), one Si(4), and one Si(5) atom. The Ni(2)-Ni(4) bond length is 2.51 Å. There are a spread of Ni(2)-Ni(3) bond distances ranging from 2.52-2.64 Å. The Ni(2)-Si(2) bond length is 2.41 Å. The Ni(2)-Si(3) bond length is 2.46 Å. The Ni(2)-Si(4) bond length is 2.29 Å. The Ni(2)-Si(5) bond length is 2.40 Å. In the seventh Ni site, Ni(3) is bonded in a 12-coordinate geometry to one Ni(1), one Ni(5), three equivalent Ni(2), three equivalent Ni(4), one Si(1), one Si(3), one Si(4), and one Si(5) atom. There are a spread of Ni(3)-Ni(4) bond distances ranging from 2.44-2.67 Å. The Ni(3)-Si(1) bond length is 2.38 Å. The Ni(3)-Si(3) bond length is 2.22 Å. The Ni(3)-Si(4) bond length is 2.37 Å. The Ni(3)-Si(5) bond length is 2.26 Å. In the eighth Ni site, Ni(4) is bonded in a 13-coordinate geometry to one Ni(2), one Ni(4), one Ni(8), two equivalent Ni(5), three equivalent Ni(3), one Si(4), one Si(5), and three equivalent Si(1) atoms. The Ni(4)-Ni(4) bond length is 2.44 Å. The Ni(4)-Si(4) bond length is 2.46 Å. The Ni(4)-Si(5) bond length is 2.62 Å. There are a spread of Ni(4)-Si(1) bond distances ranging from 2.30-2.83 Å. There are five inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to one Ni(8), two equivalent Ni(3), two equivalent Ni(5), and six equivalent Ni(4) atoms. In the second Si site, Si(2) is bonded in a 10-coordinate geometry to two equivalent Ni(2), two equivalent Ni(6), two equivalent Ni(7), and six equivalent Ni(1) atoms. In the third Si site, Si(3) is bonded in a 10-coordinate geometry to one Ni(5), three equivalent Ni(1), three equivalent Ni(2), and three equivalent Ni(3) atoms. In the fourth Si site, Si(4) is bonded in a distorted q6 geometry to one Ni(6), three equivalent Ni(2), three equivalent Ni(3), and three equivalent Ni(4) atoms. In the fifth Si site, Si(5) is bonded in a 11-coordinate geometry to one Ni(7), one Ni(8), three equivalent Ni(2), three equivalent Ni(3), and three equivalent Ni(4) atoms.