Si5O(PO4)6 crystallizes in the trigonal R-3 space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to six equivalent O(5) atoms to form SiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form SiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(3) and three equivalent O(2) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(3)O4 tetrahedra and corners with three equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Si(1)O6 octahedra, corners with two equivalent Si(2)O6 octahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 29-47°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(2) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(3) and one P(1) atom. In the third O site, O(3) is bonded in a linear geometry to two equivalent Si(3) atoms. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(2) and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom.
Si5O(PO4)6 crystallizes in the trigonal R-3 space group. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to six equivalent O(5) atoms to form SiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. All Si(1)-O(5) bond lengths are 1.76 Å. In the second Si site, Si(2) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form SiO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. All Si(2)-O(1) bond lengths are 1.74 Å. All Si(2)-O(4) bond lengths are 1.79 Å. In the third Si site, Si(3) is bonded to one O(3) and three equivalent O(2) atoms to form SiO4 tetrahedra that share  a cornercorner with one Si(3)O4 tetrahedra and corners with three equivalent P(1)O4 tetrahedra. The Si(3)-O(3) bond length is 1.59 Å. All Si(3)-O(2) bond lengths are 1.62 Å. P(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form PO4 tetrahedra that share  a cornercorner with one Si(1)O6 octahedra, corners with two equivalent Si(2)O6 octahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 29-47°. The P(1)-O(1) bond length is 1.50 Å. The P(1)-O(2) bond length is 1.57 Å. The P(1)-O(4) bond length is 1.53 Å. The P(1)-O(5) bond length is 1.50 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Si(2) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(3) and one P(1) atom. In the third O site, O(3) is bonded in a linear geometry to two equivalent Si(3) atoms. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(2) and one P(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one P(1) atom.