Mn7(PO8)2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(2), two equivalent O(7), and two equivalent O(8) atoms to form distorted MnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent Mn(2)O5 trigonal bipyramids, and edges with two equivalent Mn(2)O5 trigonal bipyramids. In the second Mn site, Mn(2) is bonded to one O(4), two equivalent O(7), and two equivalent O(8) atoms to form distorted MnO5 trigonal bipyramids that share corners with two equivalent Mn(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent Mn(2)O5 trigonal bipyramids,  an edgeedge with one Mn(1)O6 octahedra, and  an edgeedge with one Mn(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 44-73°. In the third Mn site, Mn(3) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(8) atom. In the fourth Mn site, Mn(4) is bonded to one O(1), one O(3), one O(5), and two equivalent O(6) atoms to form distorted MnO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with two equivalent Mn(4)O5 trigonal bipyramids. 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  a cornercorner with one Mn(1)O6 octahedra,  a cornercorner with one Mn(2)O5 trigonal bipyramid, and corners with two equivalent Mn(4)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 31°. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a bent 120 degrees geometry to one Mn(3) and one Mn(4) atom. In the second O site, O(6) is bonded in a bent 120 degrees geometry to two equivalent Mn(4) atoms. In the third O site, O(7) is bonded in a distorted see-saw-like geometry to one Mn(1), one Mn(3), and two equivalent Mn(2) atoms. In the fourth O site, O(8) is bonded to one Mn(1), one Mn(3), and two equivalent Mn(2) atoms to form a mixture of distorted edge and corner-sharing OMn4 trigonal pyramids. In the fifth O site, O(1) is bonded in a 3-coordinate geometry to one Mn(3), one Mn(4), and one P(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Mn(1), one Mn(3), and one P(1) atom. In the seventh O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mn(4) and one P(1) atom. In the eighth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Mn(2), one Mn(3), and one P(1) atom.
Mn7(PO8)2 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to two equivalent O(2), two equivalent O(7), and two equivalent O(8) atoms to form distorted MnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with four equivalent Mn(2)O5 trigonal bipyramids, and edges with two equivalent Mn(2)O5 trigonal bipyramids. Both Mn(1)-O(2) bond lengths are 2.48 Å. Both Mn(1)-O(7) bond lengths are 1.96 Å. Both Mn(1)-O(8) bond lengths are 1.89 Å. In the second Mn site, Mn(2) is bonded to one O(4), two equivalent O(7), and two equivalent O(8) atoms to form distorted MnO5 trigonal bipyramids that share corners with two equivalent Mn(1)O6 octahedra,  a cornercorner with one P(1)O4 tetrahedra, corners with two equivalent Mn(2)O5 trigonal bipyramids,  an edgeedge with one Mn(1)O6 octahedra, and  an edgeedge with one Mn(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 44-73°. The Mn(2)-O(4) bond length is 2.13 Å. There is one shorter (2.06 Å) and one longer (2.13 Å) Mn(2)-O(7) bond length. There is one shorter (2.07 Å) and one longer (2.08 Å) Mn(2)-O(8) bond length. In the third Mn site, Mn(3) is bonded in a 6-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(7), and one O(8) atom. The Mn(3)-O(1) bond length is 2.54 Å. The Mn(3)-O(2) bond length is 2.06 Å. The Mn(3)-O(4) bond length is 2.01 Å. The Mn(3)-O(5) bond length is 1.81 Å. The Mn(3)-O(7) bond length is 2.18 Å. The Mn(3)-O(8) bond length is 2.32 Å. In the fourth Mn site, Mn(4) is bonded to one O(1), one O(3), one O(5), and two equivalent O(6) atoms to form distorted MnO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra and corners with two equivalent Mn(4)O5 trigonal bipyramids. The Mn(4)-O(1) bond length is 1.97 Å. The Mn(4)-O(3) bond length is 2.01 Å. The Mn(4)-O(5) bond length is 1.86 Å. There is one shorter (1.81 Å) and one longer (1.89 Å) Mn(4)-O(6) bond length. 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  a cornercorner with one Mn(1)O6 octahedra,  a cornercorner with one Mn(2)O5 trigonal bipyramid, and corners with two equivalent Mn(4)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 31°. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.54 Å. The P(1)-O(4) bond length is 1.60 Å. There are eight inequivalent O sites. In the first O site, O(5) is bonded in a bent 120 degrees geometry to one Mn(3) and one Mn(4) atom. In the second O site, O(6) is bonded in a bent 120 degrees geometry to two equivalent Mn(4) atoms. In the third O site, O(7) is bonded in a distorted see-saw-like geometry to one Mn(1), one Mn(3), and two equivalent Mn(2) atoms. In the fourth O site, O(8) is bonded to one Mn(1), one Mn(3), and two equivalent Mn(2) atoms to form a mixture of distorted edge and corner-sharing OMn4 trigonal pyramids. In the fifth O site, O(1) is bonded in a 3-coordinate geometry to one Mn(3), one Mn(4), and one P(1) atom. In the sixth O site, O(2) is bonded in a 3-coordinate geometry to one Mn(1), one Mn(3), and one P(1) atom. In the seventh O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Mn(4) and one P(1) atom. In the eighth O site, O(4) is bonded in a trigonal non-coplanar geometry to one Mn(2), one Mn(3), and one P(1) atom.