Li7Fe3Ni(PO4)6 crystallizes in the trigonal R3 space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded in a 3-coordinate geometry to one O(5) and two equivalent O(2) atoms. In the second Li site, Li(2) is bonded in a distorted rectangular see-saw-like geometry to one O(3), one O(8), and two equivalent O(6) atoms. In the third Li site, Li(3) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(6) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(2) and three equivalent O(7) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. In the third Fe site, Fe(3) is bonded to three equivalent O(4) and three equivalent O(8) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. Ni(1) is bonded to three equivalent O(3) and three equivalent O(6) atoms to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-44°. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 24-47°. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the second O site, O(8) is bonded in a 3-coordinate geometry to one Li(2), one Fe(3), and one P(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Li(3), one Fe(2), and one P(1) atom. In the fourth O site, O(2) is bonded to two equivalent Li(1), one Fe(1), and one P(1) atom to form distorted edge-sharing OLi2FeP tetrahedra. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Li(2), one Ni(1), and one P(1) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(1) atom. In the seventh O site, O(5) is bonded in a 3-coordinate geometry to one Li(1), one Fe(2), and one P(2) atom. In the eighth O site, O(6) is bonded to one Li(3), two equivalent Li(2), one Ni(1), and one P(2) atom to form distorted face-sharing OLi3NiP square pyramids.
Li7Fe3Ni(PO4)6 crystallizes in the trigonal R3 space group. There are three inequivalent Li sites. In the first Li site, Li(1) is bonded in a 3-coordinate geometry to one O(5) and two equivalent O(2) atoms. The Li(1)-O(5) bond length is 2.06 Å. There is one shorter (1.97 Å) and one longer (2.09 Å) Li(1)-O(2) bond length. In the second Li site, Li(2) is bonded in a distorted rectangular see-saw-like geometry to one O(3), one O(8), and two equivalent O(6) atoms. The Li(2)-O(3) bond length is 2.02 Å. The Li(2)-O(8) bond length is 2.01 Å. There is one shorter (2.07 Å) and one longer (2.26 Å) Li(2)-O(6) bond length. In the third Li site, Li(3) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(6) atoms. All Li(3)-O(1) bond lengths are 2.47 Å. All Li(3)-O(6) bond lengths are 2.16 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(2) and three equivalent O(7) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. All Fe(1)-O(2) bond lengths are 2.06 Å. All Fe(1)-O(7) bond lengths are 1.93 Å. In the second Fe site, Fe(2) is bonded to three equivalent O(1) and three equivalent O(5) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. All Fe(2)-O(1) bond lengths are 2.02 Å. All Fe(2)-O(5) bond lengths are 2.07 Å. In the third Fe site, Fe(3) is bonded to three equivalent O(4) and three equivalent O(8) atoms to form FeO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. All Fe(3)-O(4) bond lengths are 1.96 Å. All Fe(3)-O(8) bond lengths are 2.10 Å. Ni(1) is bonded to three equivalent O(3) and three equivalent O(6) atoms to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. All Ni(1)-O(3) bond lengths are 2.00 Å. All Ni(1)-O(6) bond lengths are 2.14 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-44°. The P(1)-O(1) bond length is 1.55 Å. The P(1)-O(2) bond length is 1.57 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(4) bond length is 1.53 Å. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Fe(2)O6 octahedra,  a cornercorner with one Fe(3)O6 octahedra, and  a cornercorner with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 24-47°. The P(2)-O(5) bond length is 1.56 Å. The P(2)-O(6) bond length is 1.56 Å. The P(2)-O(7) bond length is 1.52 Å. The P(2)-O(8) bond length is 1.56 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a bent 150 degrees geometry to one Fe(1) and one P(2) atom. In the second O site, O(8) is bonded in a 3-coordinate geometry to one Li(2), one Fe(3), and one P(2) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Li(3), one Fe(2), and one P(1) atom. In the fourth O site, O(2) is bonded to two equivalent Li(1), one Fe(1), and one P(1) atom to form distorted edge-sharing OLi2FeP tetrahedra. In the fifth O site, O(3) is bonded in a 3-coordinate geometry to one Li(2), one Ni(1), and one P(1) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Fe(3) and one P(1) atom. In the seventh O site, O(5) is bonded in a 3-coordinate geometry to one Li(1), one Fe(2), and one P(2) atom. In the eighth O site, O(6) is bonded to one Li(3), two equivalent Li(2), one Ni(1), and one P(2) atom to form distorted face-sharing OLi3NiP square pyramids.