Ni6SnSe2 crystallizes in the tetragonal I4mm space group. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent Ni(2), four equivalent Ni(3), and four equivalent Sn(1) atoms to form NiNi8Sn4 cuboctahedra that share corners with four equivalent Ni(1)Ni8Sn4 cuboctahedra, faces with four equivalent Ni(1)Ni8Sn4 cuboctahedra, and faces with four equivalent Sn(1)Ni12 cuboctahedra. In the second Ni site, Ni(2) is bonded in a distorted water-like geometry to two equivalent Ni(1), two equivalent Sn(1), and two equivalent Se(1) atoms. In the third Ni site, Ni(3) is bonded in a distorted water-like geometry to two equivalent Ni(1), two equivalent Sn(1), and two equivalent Se(2) atoms. In the fourth Ni site, Ni(4) is bonded in a 5-coordinate geometry to one Se(2) and four equivalent Se(1) atoms. Sn(1) is bonded to four equivalent Ni(1), four equivalent Ni(2), and four equivalent Ni(3) atoms to form SnNi12 cuboctahedra that share corners with four equivalent Sn(1)Ni12 cuboctahedra, faces with four equivalent Ni(1)Ni8Sn4 cuboctahedra, and faces with four equivalent Sn(1)Ni12 cuboctahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 8-coordinate geometry to four equivalent Ni(2) and four equivalent Ni(4) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Ni(4) and four equivalent Ni(3) atoms.
Ni6SnSe2 crystallizes in the tetragonal I4mm space group. There are four inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to four equivalent Ni(2), four equivalent Ni(3), and four equivalent Sn(1) atoms to form NiNi8Sn4 cuboctahedra that share corners with four equivalent Ni(1)Ni8Sn4 cuboctahedra, faces with four equivalent Ni(1)Ni8Sn4 cuboctahedra, and faces with four equivalent Sn(1)Ni12 cuboctahedra. All Ni(1)-Ni(2) bond lengths are 2.64 Å. All Ni(1)-Ni(3) bond lengths are 2.65 Å. All Ni(1)-Sn(1) bond lengths are 2.61 Å. In the second Ni site, Ni(2) is bonded in a distorted water-like geometry to two equivalent Ni(1), two equivalent Sn(1), and two equivalent Se(1) atoms. Both Ni(2)-Sn(1) bond lengths are 2.64 Å. Both Ni(2)-Se(1) bond lengths are 2.43 Å. In the third Ni site, Ni(3) is bonded in a distorted water-like geometry to two equivalent Ni(1), two equivalent Sn(1), and two equivalent Se(2) atoms. Both Ni(3)-Sn(1) bond lengths are 2.66 Å. Both Ni(3)-Se(2) bond lengths are 2.33 Å. In the fourth Ni site, Ni(4) is bonded in a 5-coordinate geometry to one Se(2) and four equivalent Se(1) atoms. The Ni(4)-Se(2) bond length is 2.31 Å. All Ni(4)-Se(1) bond lengths are 2.63 Å. Sn(1) is bonded to four equivalent Ni(1), four equivalent Ni(2), and four equivalent Ni(3) atoms to form SnNi12 cuboctahedra that share corners with four equivalent Sn(1)Ni12 cuboctahedra, faces with four equivalent Ni(1)Ni8Sn4 cuboctahedra, and faces with four equivalent Sn(1)Ni12 cuboctahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 8-coordinate geometry to four equivalent Ni(2) and four equivalent Ni(4) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Ni(4) and four equivalent Ni(3) atoms.