Mg2Ti5(PO4)6 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to one O(1), one O(10), one O(11), one O(4), and one O(8) atom to form MgO5 trigonal bipyramids that share  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Ti(1)O6 octahedra, and  an edgeedge with one Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles are 63°. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(11), one O(2), one O(6), and two equivalent O(5) atoms to form TiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Ti(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. In the second Ti site, Ti(2) is bonded to one O(10), one O(12), one O(3), one O(8), and two equivalent O(7) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Ti(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 63°. In the third Ti site, Ti(3) is bonded to two equivalent O(12), two equivalent O(4), and two equivalent O(9) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(11), one O(12), one O(2), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-60°. In the second P site, P(2) is bonded to one O(10), one O(5), one O(7), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 20-56°. In the third P site, P(3) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 26-58°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one P(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Ti(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ti(2) and one P(3) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Ti(3), and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Ti(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ti(1) and one P(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ti(2) and one P(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(2), and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Ti(3) and one P(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(2), and one P(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one P(1) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Ti(2), one Ti(3), and one P(1) atom.
Mg2Ti5(PO4)6 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to one O(1), one O(10), one O(11), one O(4), and one O(8) atom to form MgO5 trigonal bipyramids that share  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one P(2)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Ti(1)O6 octahedra, and  an edgeedge with one Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles are 63°. The Mg(1)-O(1) bond length is 2.06 Å. The Mg(1)-O(10) bond length is 2.02 Å. The Mg(1)-O(11) bond length is 2.14 Å. The Mg(1)-O(4) bond length is 2.03 Å. The Mg(1)-O(8) bond length is 2.09 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(11), one O(2), one O(6), and two equivalent O(5) atoms to form TiO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra,  an edgeedge with one Ti(1)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The Ti(1)-O(1) bond length is 2.18 Å. The Ti(1)-O(11) bond length is 2.09 Å. The Ti(1)-O(2) bond length is 1.97 Å. The Ti(1)-O(6) bond length is 1.97 Å. There is one shorter (2.09 Å) and one longer (2.15 Å) Ti(1)-O(5) bond length. In the second Ti site, Ti(2) is bonded to one O(10), one O(12), one O(3), one O(8), and two equivalent O(7) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra,  a cornercorner with one P(3)O4 tetrahedra, corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra,  an edgeedge with one Ti(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 63°. The Ti(2)-O(10) bond length is 2.12 Å. The Ti(2)-O(12) bond length is 2.19 Å. The Ti(2)-O(3) bond length is 1.97 Å. The Ti(2)-O(8) bond length is 2.10 Å. Both Ti(2)-O(7) bond lengths are 2.09 Å. In the third Ti site, Ti(3) is bonded to two equivalent O(12), two equivalent O(4), and two equivalent O(9) atoms to form TiO6 octahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with two equivalent P(3)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. Both Ti(3)-O(12) bond lengths are 2.21 Å. Both Ti(3)-O(4) bond lengths are 2.23 Å. Both Ti(3)-O(9) bond lengths are 2.05 Å. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(11), one O(12), one O(2), and one O(8) atom to form PO4 tetrahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 33-60°. The P(1)-O(11) bond length is 1.56 Å. The P(1)-O(12) bond length is 1.57 Å. The P(1)-O(2) bond length is 1.52 Å. The P(1)-O(8) bond length is 1.56 Å. In the second P site, P(2) is bonded to one O(10), one O(5), one O(7), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra, and  a cornercorner with one Mg(1)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 20-56°. The P(2)-O(10) bond length is 1.55 Å. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(7) bond length is 1.56 Å. The P(2)-O(9) bond length is 1.52 Å. In the third P site, P(3) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form PO4 tetrahedra that share  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 26-58°. The P(3)-O(1) bond length is 1.57 Å. The P(3)-O(3) bond length is 1.53 Å. The P(3)-O(4) bond length is 1.57 Å. The P(3)-O(6) bond length is 1.53 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one P(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Ti(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ti(2) and one P(3) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Ti(3), and one P(3) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to two equivalent Ti(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Ti(1) and one P(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to two equivalent Ti(2) and one P(2) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(2), and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Ti(3) and one P(2) atom. In the tenth O site, O(10) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(2), and one P(2) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one P(1) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Ti(2), one Ti(3), and one P(1) atom.