SrAl3P2(HO2)7 crystallizes in the trigonal R3m space group. Sr(1) is bonded to three equivalent O(1), three equivalent O(3), three equivalent O(4), and three equivalent O(6) atoms to form SrO12 cuboctahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and faces with six equivalent Al(1)O6 octahedra. Al(1) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with four equivalent Al(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, and faces with two equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 40-46°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2) and three equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent Sr(1)O12 cuboctahedra and corners with three equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the second P site, P(2) is bonded to one O(5) and three equivalent O(6) atoms to form PO4 tetrahedra that share corners with three equivalent Sr(1)O12 cuboctahedra and corners with three equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) atom. In the third H site, H(3) is bonded in a single-bond geometry to one O(5) atom. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(1), and one P(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Sr(1), two equivalent Al(1), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Sr(1), two equivalent Al(1), and one H(2) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one P(2) and one H(3) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(1), and one P(2) atom.
SrAl3P2(HO2)7 crystallizes in the trigonal R3m space group. Sr(1) is bonded to three equivalent O(1), three equivalent O(3), three equivalent O(4), and three equivalent O(6) atoms to form SrO12 cuboctahedra that share corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and faces with six equivalent Al(1)O6 octahedra. All Sr(1)-O(1) bond lengths are 2.83 Å. All Sr(1)-O(3) bond lengths are 2.70 Å. All Sr(1)-O(4) bond lengths are 2.70 Å. All Sr(1)-O(6) bond lengths are 2.82 Å. Al(1) is bonded to one O(1), one O(6), two equivalent O(3), and two equivalent O(4) atoms to form AlO6 octahedra that share corners with four equivalent Al(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, and faces with two equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 40-46°. The Al(1)-O(1) bond length is 1.89 Å. The Al(1)-O(6) bond length is 1.94 Å. Both Al(1)-O(3) bond lengths are 1.92 Å. Both Al(1)-O(4) bond lengths are 1.94 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2) and three equivalent O(1) atoms to form PO4 tetrahedra that share corners with three equivalent Sr(1)O12 cuboctahedra and corners with three equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 52°. The P(1)-O(2) bond length is 1.54 Å. All P(1)-O(1) bond lengths are 1.56 Å. In the second P site, P(2) is bonded to one O(5) and three equivalent O(6) atoms to form PO4 tetrahedra that share corners with three equivalent Sr(1)O12 cuboctahedra and corners with three equivalent Al(1)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. The P(2)-O(5) bond length is 1.59 Å. All P(2)-O(6) bond lengths are 1.53 Å. There are three inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(3) atom. The H(1)-O(3) bond length is 1.00 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(4) atom. The H(2)-O(4) bond length is 0.97 Å. In the third H site, H(3) is bonded in a single-bond geometry to one O(5) atom. The H(3)-O(5) bond length is 0.98 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(1), and one P(1) atom. In the second O site, O(2) is bonded in a single-bond geometry to one P(1) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Sr(1), two equivalent Al(1), and one H(1) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Sr(1), two equivalent Al(1), and one H(2) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one P(2) and one H(3) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(1), and one P(2) atom.