K2MnP2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(7), two equivalent O(6), and three equivalent O(5) atoms. In the second K site, K(2) is bonded in a 9-coordinate geometry to one O(3), one O(7), two equivalent O(1), two equivalent O(2), and three equivalent O(4) atoms. Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form MnO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three 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(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 6-46°. In the second P site, P(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-41°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(1), two equivalent K(2), one Mn(1), and one P(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one K(1), two equivalent K(2), one Mn(1), and one P(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Mn(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to three equivalent K(2), one Mn(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to three equivalent K(1), one Mn(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one P(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Mn(1), and one P(2) atom.
K2MnP2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(7), two equivalent O(6), and three equivalent O(5) atoms. The K(1)-O(1) bond length is 2.92 Å. The K(1)-O(2) bond length is 2.76 Å. The K(1)-O(3) bond length is 3.00 Å. The K(1)-O(7) bond length is 2.93 Å. There is one shorter (2.90 Å) and one longer (3.00 Å) K(1)-O(6) bond length. There are a spread of K(1)-O(5) bond distances ranging from 2.92-2.97 Å. In the second K site, K(2) is bonded in a 9-coordinate geometry to one O(3), one O(7), two equivalent O(1), two equivalent O(2), and three equivalent O(4) atoms. The K(2)-O(3) bond length is 2.81 Å. The K(2)-O(7) bond length is 3.01 Å. There is one shorter (2.84 Å) and one longer (3.14 Å) K(2)-O(1) bond length. Both K(2)-O(2) bond lengths are 2.87 Å. There are a spread of K(2)-O(4) bond distances ranging from 2.84-3.03 Å. Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(7) atom to form MnO6 octahedra that share corners with three equivalent P(1)O4 tetrahedra and corners with three equivalent P(2)O4 tetrahedra. The Mn(1)-O(1) bond length is 2.23 Å. The Mn(1)-O(2) bond length is 2.30 Å. The Mn(1)-O(3) bond length is 2.19 Å. The Mn(1)-O(4) bond length is 2.22 Å. The Mn(1)-O(5) bond length is 2.23 Å. The Mn(1)-O(7) bond length is 2.19 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(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra and  a cornercorner with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 6-46°. The P(1)-O(1) bond length is 1.53 Å. The P(1)-O(2) bond length is 1.53 Å. The P(1)-O(5) bond length is 1.53 Å. The P(1)-O(6) bond length is 1.66 Å. In the second P site, P(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form PO4 tetrahedra that share corners with three equivalent Mn(1)O6 octahedra and  a cornercorner with one P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 14-41°. The P(2)-O(3) bond length is 1.54 Å. The P(2)-O(4) bond length is 1.53 Å. The P(2)-O(6) bond length is 1.66 Å. The P(2)-O(7) bond length is 1.52 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one K(1), two equivalent K(2), one Mn(1), and one P(1) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to one K(1), two equivalent K(2), one Mn(1), and one P(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one K(1), one K(2), one Mn(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to three equivalent K(2), one Mn(1), and one P(2) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to three equivalent K(1), one Mn(1), and one P(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to two equivalent K(1), one P(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), one K(2), one Mn(1), and one P(2) atom.