FeP4 is Sylvanite-derived structured and crystallizes in the monoclinic C2/c space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent P(2), two equivalent P(3), and two equivalent P(4) atoms to form FeP6 octahedra that share corners with two equivalent P(2)Fe2P2 tetrahedra and edges with two equivalent Fe(2)P6 octahedra. In the second Fe site, Fe(2) is bonded to two equivalent P(1), two equivalent P(2), and two equivalent P(4) atoms to form FeP6 octahedra that share corners with four equivalent P(2)Fe2P2 tetrahedra and edges with two equivalent Fe(1)P6 octahedra. There are four inequivalent P sites. In the first P site, P(1) is bonded in a 4-coordinate geometry to one Fe(2), one P(1), one P(2), and one P(3) atom. In the second P site, P(2) is bonded to one Fe(1), one Fe(2), one P(1), and one P(2) atom to form distorted PFe2P2 tetrahedra that share  a cornercorner with one Fe(1)P6 octahedra, corners with two equivalent Fe(2)P6 octahedra, and corners with two equivalent P(2)Fe2P2 tetrahedra. The corner-sharing octahedral tilt angles range from 50-67°. In the third P site, P(3) is bonded in a 4-coordinate geometry to one Fe(1), one P(1), one P(3), and one P(4) atom. In the fourth P site, P(4) is bonded in a 4-coordinate geometry to one Fe(1), one Fe(2), one P(3), and one P(4) atom.
FeP4 is Sylvanite-derived structured and crystallizes in the monoclinic C2/c space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent P(2), two equivalent P(3), and two equivalent P(4) atoms to form FeP6 octahedra that share corners with two equivalent P(2)Fe2P2 tetrahedra and edges with two equivalent Fe(2)P6 octahedra. Both Fe(1)-P(2) bond lengths are 2.23 Å. Both Fe(1)-P(3) bond lengths are 2.18 Å. Both Fe(1)-P(4) bond lengths are 2.26 Å. In the second Fe site, Fe(2) is bonded to two equivalent P(1), two equivalent P(2), and two equivalent P(4) atoms to form FeP6 octahedra that share corners with four equivalent P(2)Fe2P2 tetrahedra and edges with two equivalent Fe(1)P6 octahedra. Both Fe(2)-P(1) bond lengths are 2.20 Å. Both Fe(2)-P(2) bond lengths are 2.25 Å. Both Fe(2)-P(4) bond lengths are 2.32 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded in a 4-coordinate geometry to one Fe(2), one P(1), one P(2), and one P(3) atom. The P(1)-P(1) bond length is 2.28 Å. The P(1)-P(2) bond length is 2.19 Å. The P(1)-P(3) bond length is 2.24 Å. In the second P site, P(2) is bonded to one Fe(1), one Fe(2), one P(1), and one P(2) atom to form distorted PFe2P2 tetrahedra that share  a cornercorner with one Fe(1)P6 octahedra, corners with two equivalent Fe(2)P6 octahedra, and corners with two equivalent P(2)Fe2P2 tetrahedra. The corner-sharing octahedral tilt angles range from 50-67°. The P(2)-P(2) bond length is 2.25 Å. In the third P site, P(3) is bonded in a 4-coordinate geometry to one Fe(1), one P(1), one P(3), and one P(4) atom. The P(3)-P(3) bond length is 2.17 Å. The P(3)-P(4) bond length is 2.24 Å. In the fourth P site, P(4) is bonded in a 4-coordinate geometry to one Fe(1), one Fe(2), one P(3), and one P(4) atom. The P(4)-P(4) bond length is 2.25 Å.