Sb2P2O9 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(3), one O(4), one O(6), one O(7), and two equivalent O(5) atoms to form SbO6 octahedra that share corners with two equivalent Sb(2)O6 octahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. In the second Sb site, Sb(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and edges with two equivalent Sb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(6), and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with two equivalent Sb(2)O6 octahedra and corners with three equivalent Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 8-48°. In the second P site, P(2) is bonded to one O(4), one O(7), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with two equivalent Sb(2)O6 octahedra and  an edgeedge with one Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. There are seven inequivalent O sites. In the first O site, O(4) is bonded in an L-shaped geometry to one Sb(1) and one P(2) atom. In the second O site, O(5) is bonded in a bent 150 degrees geometry to one Sb(1) and one P(1) atom. In the third O site, O(6) is bonded in a linear geometry to one Sb(1) and one P(1) atom. In the fourth O site, O(7) is bonded in an L-shaped geometry to one Sb(1) and one P(2) atom. In the fifth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Sb(2) and one P(2) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Sb(2) and one P(1) atom. In the seventh O site, O(3) is bonded in a 3-coordinate geometry to one Sb(1) and two equivalent Sb(2) atoms.
Sb2P2O9 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(3), one O(4), one O(6), one O(7), and two equivalent O(5) atoms to form SbO6 octahedra that share corners with two equivalent Sb(2)O6 octahedra, corners with three equivalent P(1)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 47°. The Sb(1)-O(3) bond length is 1.95 Å. The Sb(1)-O(4) bond length is 2.04 Å. The Sb(1)-O(6) bond length is 2.00 Å. The Sb(1)-O(7) bond length is 2.00 Å. Both Sb(1)-O(5) bond lengths are 2.07 Å. In the second Sb site, Sb(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and edges with two equivalent Sb(2)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. Both Sb(2)-O(1) bond lengths are 2.22 Å. Both Sb(2)-O(2) bond lengths are 2.34 Å. Both Sb(2)-O(3) bond lengths are 2.29 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(6), and two equivalent O(5) atoms to form PO4 tetrahedra that share corners with two equivalent Sb(2)O6 octahedra and corners with three equivalent Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 8-48°. The P(1)-O(2) bond length is 1.57 Å. The P(1)-O(6) bond length is 1.54 Å. Both P(1)-O(5) bond lengths are 1.54 Å. In the second P site, P(2) is bonded to one O(4), one O(7), and two equivalent O(1) atoms to form PO4 tetrahedra that share corners with two equivalent Sb(2)O6 octahedra and  an edgeedge with one Sb(1)O6 octahedra. The corner-sharing octahedral tilt angles are 48°. The P(2)-O(4) bond length is 1.60 Å. The P(2)-O(7) bond length is 1.63 Å. Both P(2)-O(1) bond lengths are 1.53 Å. There are seven inequivalent O sites. In the first O site, O(4) is bonded in an L-shaped geometry to one Sb(1) and one P(2) atom. In the second O site, O(5) is bonded in a bent 150 degrees geometry to one Sb(1) and one P(1) atom. In the third O site, O(6) is bonded in a linear geometry to one Sb(1) and one P(1) atom. In the fourth O site, O(7) is bonded in an L-shaped geometry to one Sb(1) and one P(2) atom. In the fifth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Sb(2) and one P(2) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Sb(2) and one P(1) atom. In the seventh O site, O(3) is bonded in a 3-coordinate geometry to one Sb(1) and two equivalent Sb(2) atoms.