MgFe4(PS)4 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent Fe(1), two equivalent P(1), two equivalent P(2), and two equivalent S(2) atoms to form distorted MgFe2P4S2 hexagonal bipyramids that share corners with four equivalent S(1)Fe3P tetrahedra, corners with two equivalent P(1)MgFe3S trigonal bipyramids, and edges with four equivalent Fe(2)P3S3 octahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 7-coordinate geometry to one Mg(1), one P(1), two equivalent P(2), one S(1), and two equivalent S(2) atoms. In the second Fe site, Fe(2) is bonded to one P(2), two equivalent P(1), one S(2), and two equivalent S(1) atoms to form FeP3S3 octahedra that share corners with two equivalent S(1)Fe3P tetrahedra, corners with two equivalent P(1)MgFe3S trigonal bipyramids, edges with two equivalent Mg(1)Fe2P4S2 hexagonal bipyramids, and edges with two equivalent Fe(2)P3S3 octahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one Mg(1), one Fe(1), two equivalent Fe(2), and one S(1) atom to form distorted PMgFe3S trigonal bipyramids that share  a cornercorner with one Mg(1)Fe2P4S2 hexagonal bipyramid, corners with two equivalent Fe(2)P3S3 octahedra, corners with five equivalent S(1)Fe3P tetrahedra,  a cornercorner with one P(1)MgFe3S trigonal bipyramid, and  an edgeedge with one P(1)MgFe3S trigonal bipyramid. The corner-sharing octahedral tilt angles range from 68-72°. In the second P site, P(2) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded to one Fe(1), two equivalent Fe(2), and one P(1) atom to form SFe3P tetrahedra that share corners with two equivalent Mg(1)Fe2P4S2 hexagonal bipyramids, corners with two equivalent Fe(2)P3S3 octahedra, corners with five equivalent P(1)MgFe3S trigonal bipyramids, and  an edgeedge with one S(1)Fe3P tetrahedra. The corner-sharing octahedral tilt angles range from 70-73°. In the second S site, S(2) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms.
MgFe4(PS)4 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent Fe(1), two equivalent P(1), two equivalent P(2), and two equivalent S(2) atoms to form distorted MgFe2P4S2 hexagonal bipyramids that share corners with four equivalent S(1)Fe3P tetrahedra, corners with two equivalent P(1)MgFe3S trigonal bipyramids, and edges with four equivalent Fe(2)P3S3 octahedra. Both Mg(1)-Fe(1) bond lengths are 2.38 Å. Both Mg(1)-P(1) bond lengths are 2.58 Å. Both Mg(1)-P(2) bond lengths are 2.39 Å. Both Mg(1)-S(2) bond lengths are 2.30 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 7-coordinate geometry to one Mg(1), one P(1), two equivalent P(2), one S(1), and two equivalent S(2) atoms. The Fe(1)-P(1) bond length is 2.38 Å. There is one shorter (2.13 Å) and one longer (2.35 Å) Fe(1)-P(2) bond length. The Fe(1)-S(1) bond length is 2.23 Å. There is one shorter (2.17 Å) and one longer (2.53 Å) Fe(1)-S(2) bond length. In the second Fe site, Fe(2) is bonded to one P(2), two equivalent P(1), one S(2), and two equivalent S(1) atoms to form FeP3S3 octahedra that share corners with two equivalent S(1)Fe3P tetrahedra, corners with two equivalent P(1)MgFe3S trigonal bipyramids, edges with two equivalent Mg(1)Fe2P4S2 hexagonal bipyramids, and edges with two equivalent Fe(2)P3S3 octahedra. The Fe(2)-P(2) bond length is 2.23 Å. There is one shorter (2.36 Å) and one longer (2.39 Å) Fe(2)-P(1) bond length. The Fe(2)-S(2) bond length is 2.24 Å. There is one shorter (2.29 Å) and one longer (2.32 Å) Fe(2)-S(1) bond length. There are two inequivalent P sites. In the first P site, P(1) is bonded to one Mg(1), one Fe(1), two equivalent Fe(2), and one S(1) atom to form distorted PMgFe3S trigonal bipyramids that share  a cornercorner with one Mg(1)Fe2P4S2 hexagonal bipyramid, corners with two equivalent Fe(2)P3S3 octahedra, corners with five equivalent S(1)Fe3P tetrahedra,  a cornercorner with one P(1)MgFe3S trigonal bipyramid, and  an edgeedge with one P(1)MgFe3S trigonal bipyramid. The corner-sharing octahedral tilt angles range from 68-72°. The P(1)-S(1) bond length is 2.31 Å. In the second P site, P(2) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms. There are two inequivalent S sites. In the first S site, S(1) is bonded to one Fe(1), two equivalent Fe(2), and one P(1) atom to form SFe3P tetrahedra that share corners with two equivalent Mg(1)Fe2P4S2 hexagonal bipyramids, corners with two equivalent Fe(2)P3S3 octahedra, corners with five equivalent P(1)MgFe3S trigonal bipyramids, and  an edgeedge with one S(1)Fe3P tetrahedra. The corner-sharing octahedral tilt angles range from 70-73°. In the second S site, S(2) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms.