Mo2P4Si4O23 crystallizes in the triclinic P-1 space group. Mo(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(8), and one O(9) atom to form MoO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with three equivalent P(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(11), one O(2), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(11), one O(12), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with three equivalent Mo(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-38°. In the second P site, P(2) is bonded to one O(10), one O(4), one O(5), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Mo(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-52°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Mo(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Si(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mo(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Si(2) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Mo(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mo(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mo(1) and one P(1) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Mo(1) and one P(2) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Si(1) and one P(2) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the twelfth O site, O(12) is bonded in a linear geometry to two equivalent Si(2) atoms.
Mo2P4Si4O23 crystallizes in the triclinic P-1 space group. Mo(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(8), and one O(9) atom to form MoO6 octahedra that share corners with two equivalent P(2)O4 tetrahedra and corners with three equivalent P(1)O4 tetrahedra. The Mo(1)-O(1) bond length is 1.67 Å. The Mo(1)-O(3) bond length is 2.12 Å. The Mo(1)-O(5) bond length is 2.05 Å. The Mo(1)-O(6) bond length is 2.01 Å. The Mo(1)-O(8) bond length is 2.00 Å. The Mo(1)-O(9) bond length is 2.07 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(10), one O(11), one O(2), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one P(1)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The Si(1)-O(10) bond length is 1.62 Å. The Si(1)-O(11) bond length is 1.60 Å. The Si(1)-O(2) bond length is 1.61 Å. The Si(1)-O(7) bond length is 1.60 Å. In the second Si site, Si(2) is bonded to one O(11), one O(12), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The Si(2)-O(11) bond length is 1.59 Å. The Si(2)-O(12) bond length is 1.59 Å. The Si(2)-O(4) bond length is 1.64 Å. The Si(2)-O(7) bond length is 1.60 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(2), one O(3), one O(6), and one O(8) atom to form PO4 tetrahedra that share corners with three equivalent Mo(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 23-38°. The P(1)-O(2) bond length is 1.58 Å. The P(1)-O(3) bond length is 1.50 Å. The P(1)-O(6) bond length is 1.52 Å. The P(1)-O(8) bond length is 1.52 Å. In the second P site, P(2) is bonded to one O(10), one O(4), one O(5), and one O(9) atom to form PO4 tetrahedra that share corners with two equivalent Mo(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-52°. The P(2)-O(10) bond length is 1.54 Å. The P(2)-O(4) bond length is 1.56 Å. The P(2)-O(5) bond length is 1.50 Å. The P(2)-O(9) bond length is 1.51 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Mo(1) atom. In the second O site, O(2) is bonded in a bent 120 degrees geometry to one Si(1) and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Mo(1) and one P(1) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Si(2) and one P(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Mo(1) and one P(2) atom. In the sixth O site, O(6) is bonded in a bent 150 degrees geometry to one Mo(1) and one P(1) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mo(1) and one P(1) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Mo(1) and one P(2) atom. In the tenth O site, O(10) is bonded in a linear geometry to one Si(1) and one P(2) atom. In the eleventh O site, O(11) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the twelfth O site, O(12) is bonded in a linear geometry to two equivalent Si(2) atoms.