TiNi(PO4)2 crystallizes in the trigonal R3 space group. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(4) and three equivalent O(8) atoms to form TiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. In the second Ti site, Ti(2) is bonded to three equivalent O(2) and three equivalent O(5) atoms to form TiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Ni(1)O6 octahedra. In the third Ti site, Ti(3) is bonded to three equivalent O(1) and three equivalent O(7) atoms to form distorted TiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  a faceface with one Ti(2)O6 octahedra, and  a faceface with one Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to three equivalent O(3) and three equivalent O(6) atoms to form NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Ni(1)O6 octahedra. In the third Ni site, Ni(3) is bonded in a 6-coordinate geometry to three equivalent O(4) and three equivalent O(7) atoms. 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 Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one Ni(1)O6 octahedra, and  a cornercorner with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-52°. 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 Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one Ni(1)O6 octahedra, and  a cornercorner with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 24-52°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Ti(3) and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ti(2), one Ni(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ni(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ti(1), one Ni(3), and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Ti(2) and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ni(1), one Ni(2), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ti(3), one Ni(3), and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Ti(1) and one P(2) atom.
TiNi(PO4)2 crystallizes in the trigonal R3 space group. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(4) and three equivalent O(8) atoms to form TiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. All Ti(1)-O(4) bond lengths are 2.03 Å. All Ti(1)-O(8) bond lengths are 1.88 Å. In the second Ti site, Ti(2) is bonded to three equivalent O(2) and three equivalent O(5) atoms to form TiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Ni(1)O6 octahedra. All Ti(2)-O(2) bond lengths are 2.05 Å. All Ti(2)-O(5) bond lengths are 1.90 Å. In the third Ti site, Ti(3) is bonded to three equivalent O(1) and three equivalent O(7) atoms to form distorted TiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. All Ti(3)-O(1) bond lengths are 1.87 Å. All Ti(3)-O(7) bond lengths are 2.08 Å. There are three inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to three equivalent O(2) and three equivalent O(6) atoms to form distorted NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  a faceface with one Ti(2)O6 octahedra, and  a faceface with one Ni(2)O6 octahedra. All Ni(1)-O(2) bond lengths are 2.17 Å. All Ni(1)-O(6) bond lengths are 2.10 Å. In the second Ni site, Ni(2) is bonded to three equivalent O(3) and three equivalent O(6) atoms to form NiO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  a faceface with one Ni(1)O6 octahedra. All Ni(2)-O(3) bond lengths are 1.98 Å. All Ni(2)-O(6) bond lengths are 2.09 Å. In the third Ni site, Ni(3) is bonded in a 6-coordinate geometry to three equivalent O(4) and three equivalent O(7) atoms. All Ni(3)-O(4) bond lengths are 2.16 Å. All Ni(3)-O(7) bond lengths are 2.15 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 Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one Ni(1)O6 octahedra, and  a cornercorner with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-52°. The P(1)-O(1) bond length is 1.57 Å. The P(1)-O(2) bond length is 1.57 Å. The P(1)-O(3) bond length is 1.49 Å. The P(1)-O(4) bond length is 1.57 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 Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one Ni(1)O6 octahedra, and  a cornercorner with one Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 24-52°. The P(2)-O(5) bond length is 1.55 Å. The P(2)-O(6) bond length is 1.53 Å. The P(2)-O(7) bond length is 1.56 Å. The P(2)-O(8) bond length is 1.55 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Ti(3) and one P(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ti(2), one Ni(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ni(2) and one P(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ti(1), one Ni(3), and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Ti(2) and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Ni(1), one Ni(2), and one P(2) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ti(3), one Ni(3), and one P(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Ti(1) and one P(2) atom.