Ni4N2Se3 crystallizes in the orthorhombic Pnma space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent N(1) and two equivalent Se(2) atoms. In the second Ni site, Ni(2) is bonded to two equivalent N(1) and two equivalent Se(1) atoms to form distorted corner-sharing NiSe2N2 tetrahedra. In the third Ni site, Ni(3) is bonded in a 6-coordinate geometry to two equivalent N(1), one Se(1), and three equivalent Se(2) atoms. N(1) is bonded to one Ni(1), one Ni(2), and two equivalent Ni(3) atoms to form distorted NNi4 tetrahedra that share corners with four equivalent Se(1)Ni4 tetrahedra, corners with six equivalent Se(2)Ni4 tetrahedra,  an edgeedge with one Se(2)Ni4 tetrahedra, and edges with two equivalent N(1)Ni4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ni(2) and two equivalent Ni(3) atoms to form SeNi4 tetrahedra that share corners with two equivalent Se(1)Ni4 tetrahedra, corners with six equivalent Se(2)Ni4 tetrahedra, and corners with eight equivalent N(1)Ni4 tetrahedra. In the second Se site, Se(2) is bonded to one Ni(1) and three equivalent Ni(3) atoms to form distorted SeNi4 tetrahedra that share corners with three equivalent Se(1)Ni4 tetrahedra, corners with five equivalent Se(2)Ni4 tetrahedra, corners with six equivalent N(1)Ni4 tetrahedra,  an edgeedge with one N(1)Ni4 tetrahedra, and  an edgeedge with one Se(2)Ni4 tetrahedra.
Ni4N2Se3 crystallizes in the orthorhombic Pnma space group. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent N(1) and two equivalent Se(2) atoms. Both Ni(1)-N(1) bond lengths are 1.88 Å. Both Ni(1)-Se(2) bond lengths are 2.37 Å. In the second Ni site, Ni(2) is bonded to two equivalent N(1) and two equivalent Se(1) atoms to form distorted corner-sharing NiSe2N2 tetrahedra. Both Ni(2)-N(1) bond lengths are 1.83 Å. There is one shorter (2.28 Å) and one longer (2.43 Å) Ni(2)-Se(1) bond length. In the third Ni site, Ni(3) is bonded in a 6-coordinate geometry to two equivalent N(1), one Se(1), and three equivalent Se(2) atoms. There is one shorter (1.90 Å) and one longer (1.92 Å) Ni(3)-N(1) bond length. The Ni(3)-Se(1) bond length is 2.44 Å. There are a spread of Ni(3)-Se(2) bond distances ranging from 2.47-2.53 Å. N(1) is bonded to one Ni(1), one Ni(2), and two equivalent Ni(3) atoms to form distorted NNi4 tetrahedra that share corners with four equivalent Se(1)Ni4 tetrahedra, corners with six equivalent Se(2)Ni4 tetrahedra,  an edgeedge with one Se(2)Ni4 tetrahedra, and edges with two equivalent N(1)Ni4 tetrahedra. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded to two equivalent Ni(2) and two equivalent Ni(3) atoms to form SeNi4 tetrahedra that share corners with two equivalent Se(1)Ni4 tetrahedra, corners with six equivalent Se(2)Ni4 tetrahedra, and corners with eight equivalent N(1)Ni4 tetrahedra. In the second Se site, Se(2) is bonded to one Ni(1) and three equivalent Ni(3) atoms to form distorted SeNi4 tetrahedra that share corners with three equivalent Se(1)Ni4 tetrahedra, corners with five equivalent Se(2)Ni4 tetrahedra, corners with six equivalent N(1)Ni4 tetrahedra,  an edgeedge with one N(1)Ni4 tetrahedra, and  an edgeedge with one Se(2)Ni4 tetrahedra.