Mn2Si(P2O7)2 crystallizes in the monoclinic C2/c space group. Mn(1) is bonded to one O(3), one O(6), two equivalent O(2), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  an edgeedge with one Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 62°. Si(1) is bonded to two equivalent O(1) and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with two equivalent P(1)O4 tetrahedra and corners with two equivalent P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 37-55°. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-62°. There are seven inequivalent O sites. In the first O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one P(1) atom. In the second O site, O(3) is bonded in a bent 150 degrees geometry to one Mn(1) and one P(1) atom. In the third O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the fifth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mn(1) and one P(2) atom. In the sixth O site, O(7) is bonded in a trigonal planar geometry to two equivalent Mn(1) and one P(2) atom. In the seventh O site, O(1) is bonded in a linear geometry to one Si(1) and one P(1) atom.
Mn2Si(P2O7)2 crystallizes in the monoclinic C2/c space group. Mn(1) is bonded to one O(3), one O(6), two equivalent O(2), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with three equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and  an edgeedge with one Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles are 62°. The Mn(1)-O(3) bond length is 2.12 Å. The Mn(1)-O(6) bond length is 2.11 Å. There is one shorter (2.25 Å) and one longer (2.29 Å) Mn(1)-O(2) bond length. There is one shorter (2.28 Å) and one longer (2.31 Å) Mn(1)-O(7) bond length. Si(1) is bonded to two equivalent O(1) and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with two equivalent P(1)O4 tetrahedra and corners with two equivalent P(2)O4 tetrahedra. Both Si(1)-O(1) bond lengths are 1.61 Å. Both Si(1)-O(5) bond lengths are 1.63 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 37-55°. The P(1)-O(1) bond length is 1.57 Å. The P(1)-O(2) bond length is 1.51 Å. The P(1)-O(3) bond length is 1.51 Å. The P(1)-O(4) bond length is 1.62 Å. In the second P site, P(2) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-62°. The P(2)-O(4) bond length is 1.61 Å. The P(2)-O(5) bond length is 1.59 Å. The P(2)-O(6) bond length is 1.51 Å. The P(2)-O(7) bond length is 1.52 Å. There are seven inequivalent O sites. In the first O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mn(1) and one P(1) atom. In the second O site, O(3) is bonded in a bent 150 degrees geometry to one Mn(1) and one P(1) atom. In the third O site, O(4) is bonded in a bent 120 degrees geometry to one P(1) and one P(2) atom. In the fourth O site, O(5) is bonded in a bent 150 degrees geometry to one Si(1) and one P(2) atom. In the fifth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mn(1) and one P(2) atom. In the sixth O site, O(7) is bonded in a trigonal planar geometry to two equivalent Mn(1) and one P(2) atom. In the seventh O site, O(1) is bonded in a linear geometry to one Si(1) and one P(1) atom.