FeV2Se4 crystallizes in the monoclinic C2/m space group. V(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form distorted VSe6 octahedra that share corners with six equivalent Fe(1)Se6 octahedra, edges with six equivalent V(1)Se6 octahedra, and  a faceface with one Fe(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. Fe(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form FeSe6 octahedra that share corners with twelve equivalent V(1)Se6 octahedra, edges with two equivalent Fe(1)Se6 octahedra, and faces with two equivalent V(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded in a 5-coordinate geometry to three equivalent V(1) and two equivalent Fe(1) atoms. In the second Se site, Se(1) is bonded in a 4-coordinate geometry to three equivalent V(1) and one Fe(1) atom.
FeV2Se4 crystallizes in the monoclinic C2/m space group. V(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form distorted VSe6 octahedra that share corners with six equivalent Fe(1)Se6 octahedra, edges with six equivalent V(1)Se6 octahedra, and  a faceface with one Fe(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. There is one shorter (2.44 Å) and two longer (2.45 Å) V(1)-Se(1) bond lengths. There are two shorter (2.59 Å) and one longer (2.72 Å) V(1)-Se(2) bond length. Fe(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form FeSe6 octahedra that share corners with twelve equivalent V(1)Se6 octahedra, edges with two equivalent Fe(1)Se6 octahedra, and faces with two equivalent V(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-56°. Both Fe(1)-Se(1) bond lengths are 2.46 Å. All Fe(1)-Se(2) bond lengths are 2.55 Å. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded in a 5-coordinate geometry to three equivalent V(1) and two equivalent Fe(1) atoms. In the second Se site, Se(1) is bonded in a 4-coordinate geometry to three equivalent V(1) and one Fe(1) atom.