Y2Mn3O9 crystallizes in the hexagonal P6_3 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one O(1), three equivalent O(4), and three equivalent O(5) atoms. In the second Y site, Y(2) is bonded to one O(3), three equivalent O(4), and three equivalent O(5) atoms to form distorted YO7 pentagonal bipyramids that share corners with three equivalent Mn(1)O5 trigonal bipyramids and edges with three equivalent Mn(1)O5 trigonal bipyramids. Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form MnO5 trigonal bipyramids that share  a cornercorner with one Y(2)O7 pentagonal bipyramid, corners with six equivalent Mn(1)O5 trigonal bipyramids, and  an edgeedge with one Y(2)O7 pentagonal bipyramid. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Y(1) and three equivalent Mn(1) atoms to form distorted corner-sharing OYMn3 trigonal pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to three equivalent Mn(1) atoms. In the third O site, O(3) is bonded to one Y(2) and three equivalent Mn(1) atoms to form distorted corner-sharing OYMn3 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Mn(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Mn(1) atom.
Y2Mn3O9 crystallizes in the hexagonal P6_3 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one O(1), three equivalent O(4), and three equivalent O(5) atoms. The Y(1)-O(1) bond length is 2.57 Å. All Y(1)-O(4) bond lengths are 2.29 Å. All Y(1)-O(5) bond lengths are 2.26 Å. In the second Y site, Y(2) is bonded to one O(3), three equivalent O(4), and three equivalent O(5) atoms to form distorted YO7 pentagonal bipyramids that share corners with three equivalent Mn(1)O5 trigonal bipyramids and edges with three equivalent Mn(1)O5 trigonal bipyramids. The Y(2)-O(3) bond length is 2.42 Å. All Y(2)-O(4) bond lengths are 2.32 Å. All Y(2)-O(5) bond lengths are 2.27 Å. Mn(1) is bonded to one O(1), one O(2), one O(3), one O(4), and one O(5) atom to form MnO5 trigonal bipyramids that share  a cornercorner with one Y(2)O7 pentagonal bipyramid, corners with six equivalent Mn(1)O5 trigonal bipyramids, and  an edgeedge with one Y(2)O7 pentagonal bipyramid. The Mn(1)-O(1) bond length is 2.05 Å. The Mn(1)-O(2) bond length is 2.01 Å. The Mn(1)-O(3) bond length is 2.04 Å. The Mn(1)-O(4) bond length is 1.85 Å. The Mn(1)-O(5) bond length is 1.86 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Y(1) and three equivalent Mn(1) atoms to form distorted corner-sharing OYMn3 trigonal pyramids. In the second O site, O(2) is bonded in a trigonal planar geometry to three equivalent Mn(1) atoms. In the third O site, O(3) is bonded to one Y(2) and three equivalent Mn(1) atoms to form distorted corner-sharing OYMn3 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Mn(1) atom. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Y(1), one Y(2), and one Mn(1) atom.