SrFeNi2(PO4)3 crystallizes in the orthorhombic Imma space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Fe(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Ni(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with four equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. Ni(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-56°. In the second P site, P(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and  an edgeedge with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-51°. There are four inequivalent O sites. In the first O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), two equivalent Ni(1), and one P(1) atom. In the second O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Ni(1), and one P(2) atom. In the third O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(1), one Ni(1), and one P(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Sr(1), one Fe(1), and one P(1) atom.
SrFeNi2(PO4)3 crystallizes in the orthorhombic Imma space group. Sr(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(3) atoms. Both Sr(1)-O(1) bond lengths are 2.64 Å. Both Sr(1)-O(2) bond lengths are 2.64 Å. All Sr(1)-O(3) bond lengths are 2.66 Å. Fe(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form FeO6 octahedra that share corners with four equivalent Ni(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with four equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. Both Fe(1)-O(1) bond lengths are 2.07 Å. All Fe(1)-O(4) bond lengths are 1.97 Å. Ni(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Ni(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. Both Ni(1)-O(2) bond lengths are 2.05 Å. Both Ni(1)-O(3) bond lengths are 2.09 Å. Both Ni(1)-O(4) bond lengths are 2.05 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra and corners with four equivalent Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 45-56°. Both P(1)-O(1) bond lengths are 1.53 Å. Both P(1)-O(2) bond lengths are 1.55 Å. In the second P site, P(2) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Ni(1)O6 octahedra, and  an edgeedge with one Ni(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-51°. Both P(2)-O(3) bond lengths are 1.52 Å. Both P(2)-O(4) bond lengths are 1.57 Å. There are four inequivalent O sites. In the first O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), two equivalent Ni(1), and one P(1) atom. In the second O site, O(3) is bonded in a 3-coordinate geometry to one Sr(1), one Ni(1), and one P(2) atom. In the third O site, O(4) is bonded in a distorted trigonal planar geometry to one Fe(1), one Ni(1), and one P(2) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Sr(1), one Fe(1), and one P(1) atom.