Fe4N2Se3 crystallizes in the orthorhombic Pnnm space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 2-coordinate geometry to two equivalent N(1), two equivalent Se(1), and two equivalent Se(2) atoms. In the second Fe site, Fe(2) is bonded in a distorted bent 120 degrees geometry to two equivalent N(1), one Se(1), and three equivalent Se(2) atoms. N(1) is bonded to two equivalent Fe(1) and two equivalent Fe(2) atoms to form NFe4 tetrahedra that share corners with two equivalent N(1)Fe4 tetrahedra, corners with four equivalent Se(2)Fe5 trigonal bipyramids,  an edgeedge with one N(1)Fe4 tetrahedra, and edges with three equivalent Se(2)Fe5 trigonal bipyramids. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Fe(2) and four equivalent Fe(1) atoms. In the second Se site, Se(2) is bonded to two equivalent Fe(1) and three equivalent Fe(2) atoms to form distorted SeFe5 trigonal bipyramids that share corners with four equivalent N(1)Fe4 tetrahedra, corners with four equivalent Se(2)Fe5 trigonal bipyramids, edges with three equivalent N(1)Fe4 tetrahedra, and edges with two equivalent Se(2)Fe5 trigonal bipyramids.
Fe4N2Se3 crystallizes in the orthorhombic Pnnm space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 2-coordinate geometry to two equivalent N(1), two equivalent Se(1), and two equivalent Se(2) atoms. There is one shorter (1.81 Å) and one longer (1.91 Å) Fe(1)-N(1) bond length. Both Fe(1)-Se(1) bond lengths are 2.68 Å. Both Fe(1)-Se(2) bond lengths are 2.45 Å. In the second Fe site, Fe(2) is bonded in a distorted bent 120 degrees geometry to two equivalent N(1), one Se(1), and three equivalent Se(2) atoms. Both Fe(2)-N(1) bond lengths are 1.83 Å. The Fe(2)-Se(1) bond length is 2.53 Å. There is one shorter (2.46 Å) and two longer (2.51 Å) Fe(2)-Se(2) bond lengths. N(1) is bonded to two equivalent Fe(1) and two equivalent Fe(2) atoms to form NFe4 tetrahedra that share corners with two equivalent N(1)Fe4 tetrahedra, corners with four equivalent Se(2)Fe5 trigonal bipyramids,  an edgeedge with one N(1)Fe4 tetrahedra, and edges with three equivalent Se(2)Fe5 trigonal bipyramids. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Fe(2) and four equivalent Fe(1) atoms. In the second Se site, Se(2) is bonded to two equivalent Fe(1) and three equivalent Fe(2) atoms to form distorted SeFe5 trigonal bipyramids that share corners with four equivalent N(1)Fe4 tetrahedra, corners with four equivalent Se(2)Fe5 trigonal bipyramids, edges with three equivalent N(1)Fe4 tetrahedra, and edges with two equivalent Se(2)Fe5 trigonal bipyramids.