NiSeO4 crystallizes in the orthorhombic Cmcm space group. Ni(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NiO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and edges with two equivalent Ni(1)O6 octahedra. Se(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SeO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-55°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Ni(1) and one Se(1) atom.
NiSeO4 crystallizes in the orthorhombic Cmcm space group. Ni(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NiO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra and edges with two equivalent Ni(1)O6 octahedra. Both Ni(1)-O(2) bond lengths are 2.00 Å. All Ni(1)-O(1) bond lengths are 2.09 Å. Se(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SeO4 tetrahedra that share corners with six equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-55°. Both Se(1)-O(1) bond lengths are 1.69 Å. Both Se(1)-O(2) bond lengths are 1.64 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to two equivalent Ni(1) and one Se(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Ni(1) and one Se(1) atom.