Ni3Se4 is Hausmannite structured and crystallizes in the orthorhombic Imma space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form corner-sharing NiSe4 tetrahedra. The corner-sharing octahedral tilt angles range from 57-58°. In the second Ni site, Ni(2) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form NiSe6 octahedra that share corners with six equivalent Ni(1)Se4 tetrahedra, edges with two equivalent Ni(2)Se6 octahedra, and edges with four equivalent Ni(3)Se6 octahedra. In the third Ni site, Ni(3) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NiSe6 octahedra that share corners with six equivalent Ni(1)Se4 tetrahedra, edges with two equivalent Ni(3)Se6 octahedra, and edges with four equivalent Ni(2)Se6 octahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Ni(1), one Ni(2), and two equivalent Ni(3) atoms to form a mixture of distorted corner and edge-sharing SeNi4 trigonal pyramids. In the second Se site, Se(2) is bonded to one Ni(1), one Ni(3), and two equivalent Ni(2) atoms to form a mixture of distorted corner and edge-sharing SeNi4 trigonal pyramids.
Ni3Se4 is Hausmannite structured and crystallizes in the orthorhombic Imma space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form corner-sharing NiSe4 tetrahedra. The corner-sharing octahedral tilt angles range from 57-58°. Both Ni(1)-Se(1) bond lengths are 2.29 Å. Both Ni(1)-Se(2) bond lengths are 2.29 Å. In the second Ni site, Ni(2) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form NiSe6 octahedra that share corners with six equivalent Ni(1)Se4 tetrahedra, edges with two equivalent Ni(2)Se6 octahedra, and edges with four equivalent Ni(3)Se6 octahedra. Both Ni(2)-Se(1) bond lengths are 2.40 Å. All Ni(2)-Se(2) bond lengths are 2.40 Å. In the third Ni site, Ni(3) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form NiSe6 octahedra that share corners with six equivalent Ni(1)Se4 tetrahedra, edges with two equivalent Ni(3)Se6 octahedra, and edges with four equivalent Ni(2)Se6 octahedra. Both Ni(3)-Se(2) bond lengths are 2.41 Å. All Ni(3)-Se(1) bond lengths are 2.40 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to one Ni(1), one Ni(2), and two equivalent Ni(3) atoms to form a mixture of distorted corner and edge-sharing SeNi4 trigonal pyramids. In the second Se site, Se(2) is bonded to one Ni(1), one Ni(3), and two equivalent Ni(2) atoms to form a mixture of distorted corner and edge-sharing SeNi4 trigonal pyramids.