Ba2P6O17 crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded to one O(1), one O(4), one O(6), one O(8), and two equivalent O(5) atoms to form BaO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(3)O4 tetrahedra, and  an edgeedge with one Ba(1)O6 octahedra. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(7), one O(8), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ba(1)O6 octahedra,  a cornercorner with one P(3)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 34°. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Ba(1)O6 octahedra and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-42°. In the third P site, P(3) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Ba(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-54°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one P(2) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent P(3) atoms. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Ba(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(3) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one P(3) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one P(1) and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom.
Ba2P6O17 crystallizes in the monoclinic P2_1/c space group. Ba(1) is bonded to one O(1), one O(4), one O(6), one O(8), and two equivalent O(5) atoms to form BaO6 octahedra that share  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, corners with three equivalent P(3)O4 tetrahedra, and  an edgeedge with one Ba(1)O6 octahedra. The Ba(1)-O(1) bond length is 2.62 Å. The Ba(1)-O(4) bond length is 2.59 Å. The Ba(1)-O(6) bond length is 2.59 Å. The Ba(1)-O(8) bond length is 2.64 Å. There is one shorter (2.78 Å) and one longer (2.86 Å) Ba(1)-O(5) bond length. There are three inequivalent P sites. In the first P site, P(1) is bonded to one O(3), one O(7), one O(8), and one O(9) atom to form PO4 tetrahedra that share  a cornercorner with one Ba(1)O6 octahedra,  a cornercorner with one P(3)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 34°. The P(1)-O(3) bond length is 1.59 Å. The P(1)-O(7) bond length is 1.60 Å. The P(1)-O(8) bond length is 1.48 Å. The P(1)-O(9) bond length is 1.58 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(4), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Ba(1)O6 octahedra and corners with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-42°. The P(2)-O(1) bond length is 1.49 Å. The P(2)-O(3) bond length is 1.65 Å. The P(2)-O(4) bond length is 1.49 Å. The P(2)-O(9) bond length is 1.64 Å. In the third P site, P(3) is bonded to one O(2), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Ba(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, and  a cornercorner with one P(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 38-54°. The P(3)-O(2) bond length is 1.60 Å. The P(3)-O(5) bond length is 1.50 Å. The P(3)-O(6) bond length is 1.49 Å. The P(3)-O(7) bond length is 1.66 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one P(2) atom. In the second O site, O(2) is bonded in a linear geometry to two equivalent P(3) atoms. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted linear geometry to one Ba(1) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(3) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one P(3) atom. In the seventh O site, O(7) is bonded in a bent 120 degrees geometry to one P(1) and one P(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Ba(1) and one P(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom.