Li4MnP2O9 crystallizes in the monoclinic C2/m space group. There are four inequivalent Li sites. In the first Li site, Li(1) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(7), and two equivalent O(4) atoms. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(7), and two equivalent O(6) atoms. In the third Li site, Li(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form distorted LiO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, edges with two equivalent Li(3)O6 octahedra, and edges with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 61°. In the fourth Li site, Li(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted LiO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent P(2)O4 tetrahedra, edges with two equivalent Li(4)O6 octahedra, and edges with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. Mn(1) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with two equivalent Li(3)O6 octahedra, corners with two equivalent Li(4)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-61°. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with two equivalent Li(3)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Li(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. In the second P site, P(2) is bonded to one O(2), one O(3), and two equivalent O(6) atoms to form PO4 tetrahedra that share corners with two equivalent Li(4)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Li(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-61°. There are seven inequivalent O sites. In the first O site, O(5) is bonded to one Li(2), two equivalent Li(3), and one P(1) atom to form distorted OLi3P trigonal pyramids that share  a cornercorner with one O(7)Li2Mn2 tetrahedra and corners with two equivalent O(5)Li3P trigonal pyramids. In the second O site, O(6) is bonded in a 4-coordinate geometry to one Li(2), one Li(3), one Mn(1), and one P(2) atom. In the third O site, O(7) is bonded to one Li(1), one Li(2), and two equivalent Mn(1) atoms to form OLi2Mn2 tetrahedra that share corners with two equivalent O(7)Li2Mn2 tetrahedra,  a cornercorner with one O(2)Li3P trigonal pyramid, and  a cornercorner with one O(5)Li3P trigonal pyramid. In the fourth O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Li(2), two equivalent Li(4), and one P(1) atom. In the fifth O site, O(2) is bonded to one Li(1), two equivalent Li(4), and one P(2) atom to form distorted OLi3P trigonal pyramids that share  a cornercorner with one O(7)Li2Mn2 tetrahedra and  an edgeedge with one O(2)Li3P trigonal pyramid. In the sixth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Li(1), two equivalent Li(3), and one P(2) atom. In the seventh O site, O(4) is bonded in a 4-coordinate geometry to one Li(1), one Li(4), one Mn(1), and one P(1) atom.
Li4MnP2O9 crystallizes in the monoclinic C2/m space group. There are four inequivalent Li sites. In the first Li site, Li(1) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(7), and two equivalent O(4) atoms. The Li(1)-O(2) bond length is 1.99 Å. The Li(1)-O(3) bond length is 1.85 Å. The Li(1)-O(7) bond length is 2.06 Å. Both Li(1)-O(4) bond lengths are 2.26 Å. In the second Li site, Li(2) is bonded in a 5-coordinate geometry to one O(1), one O(5), one O(7), and two equivalent O(6) atoms. The Li(2)-O(1) bond length is 1.88 Å. The Li(2)-O(5) bond length is 1.96 Å. The Li(2)-O(7) bond length is 2.23 Å. Both Li(2)-O(6) bond lengths are 2.23 Å. In the third Li site, Li(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms to form distorted LiO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, edges with two equivalent Li(3)O6 octahedra, and edges with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 61°. Both Li(3)-O(3) bond lengths are 2.43 Å. Both Li(3)-O(5) bond lengths are 2.21 Å. Both Li(3)-O(6) bond lengths are 2.15 Å. In the fourth Li site, Li(4) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted LiO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent P(2)O4 tetrahedra, edges with two equivalent Li(4)O6 octahedra, and edges with two equivalent P(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. Both Li(4)-O(1) bond lengths are 2.42 Å. Both Li(4)-O(2) bond lengths are 2.15 Å. Both Li(4)-O(4) bond lengths are 2.09 Å. Mn(1) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(7) atoms to form MnO6 octahedra that share corners with two equivalent Li(3)O6 octahedra, corners with two equivalent Li(4)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, corners with two equivalent P(1)O4 tetrahedra, and corners with two equivalent P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-61°. Both Mn(1)-O(4) bond lengths are 1.95 Å. Both Mn(1)-O(6) bond lengths are 1.93 Å. Both Mn(1)-O(7) bond lengths are 1.86 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form PO4 tetrahedra that share corners with two equivalent Li(3)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Li(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-62°. The P(1)-O(1) bond length is 1.51 Å. The P(1)-O(5) bond length is 1.53 Å. Both P(1)-O(4) bond lengths are 1.59 Å. In the second P site, P(2) is bonded to one O(2), one O(3), and two equivalent O(6) atoms to form PO4 tetrahedra that share corners with two equivalent Li(4)O6 octahedra, corners with two equivalent Mn(1)O6 octahedra, and edges with two equivalent Li(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 51-61°. The P(2)-O(2) bond length is 1.52 Å. The P(2)-O(3) bond length is 1.51 Å. Both P(2)-O(6) bond lengths are 1.59 Å. There are seven inequivalent O sites. In the first O site, O(5) is bonded to one Li(2), two equivalent Li(3), and one P(1) atom to form distorted OLi3P trigonal pyramids that share  a cornercorner with one O(7)Li2Mn2 tetrahedra and corners with two equivalent O(5)Li3P trigonal pyramids. In the second O site, O(6) is bonded in a 4-coordinate geometry to one Li(2), one Li(3), one Mn(1), and one P(2) atom. In the third O site, O(7) is bonded to one Li(1), one Li(2), and two equivalent Mn(1) atoms to form OLi2Mn2 tetrahedra that share corners with two equivalent O(7)Li2Mn2 tetrahedra,  a cornercorner with one O(2)Li3P trigonal pyramid, and  a cornercorner with one O(5)Li3P trigonal pyramid. In the fourth O site, O(1) is bonded in a distorted rectangular see-saw-like geometry to one Li(2), two equivalent Li(4), and one P(1) atom. In the fifth O site, O(2) is bonded to one Li(1), two equivalent Li(4), and one P(2) atom to form distorted OLi3P trigonal pyramids that share  a cornercorner with one O(7)Li2Mn2 tetrahedra and  an edgeedge with one O(2)Li3P trigonal pyramid. In the sixth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Li(1), two equivalent Li(3), and one P(2) atom. In the seventh O site, O(4) is bonded in a 4-coordinate geometry to one Li(1), one Li(4), one Mn(1), and one P(1) atom.