ErMnO3 crystallizes in the hexagonal P6_3cm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one O(1), three equivalent O(3), and three equivalent O(4) atoms. In the second Er site, Er(2) is bonded to one O(2), three equivalent O(3), and three equivalent O(4) atoms to form distorted ErO7 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(2), one O(3), one O(4), and two equivalent O(1) atoms to form MnO5 trigonal bipyramids that share  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with six equivalent Mn(1)O5 trigonal bipyramids, and  an edgeedge with one Er(2)O7 pentagonal bipyramid. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Er(1) and three equivalent Mn(1) atoms to form OErMn3 trigonal pyramids that share corners with six equivalent O(3)Er3Mn tetrahedra, corners with three equivalent O(1)ErMn3 trigonal pyramids, corners with three equivalent O(2)ErMn3 trigonal pyramids, and edges with three equivalent O(4)Er3Mn tetrahedra. In the second O site, O(2) is bonded to one Er(2) and three equivalent Mn(1) atoms to form OErMn3 trigonal pyramids that share corners with six equivalent O(4)Er3Mn tetrahedra, corners with six equivalent O(1)ErMn3 trigonal pyramids, and edges with three equivalent O(3)Er3Mn tetrahedra. In the third O site, O(3) is bonded to one Er(2), two equivalent Er(1), and one Mn(1) atom to form distorted OEr3Mn tetrahedra that share corners with four equivalent O(4)Er3Mn tetrahedra, corners with six equivalent O(3)Er3Mn tetrahedra, corners with four equivalent O(1)ErMn3 trigonal pyramids, edges with three equivalent O(4)Er3Mn tetrahedra, and  an edgeedge with one O(2)ErMn3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Er(2), two equivalent Er(1), and one Mn(1) atom to form OEr3Mn tetrahedra that share corners with four equivalent O(3)Er3Mn tetrahedra, corners with six equivalent O(4)Er3Mn tetrahedra, corners with two equivalent O(2)ErMn3 trigonal pyramids, edges with three equivalent O(3)Er3Mn tetrahedra, and edges with two equivalent O(1)ErMn3 trigonal pyramids.
ErMnO3 crystallizes in the hexagonal P6_3cm space group. There are two inequivalent Er sites. In the first Er site, Er(1) is bonded in a 7-coordinate geometry to one O(1), three equivalent O(3), and three equivalent O(4) atoms. The Er(1)-O(1) bond length is 2.40 Å. All Er(1)-O(3) bond lengths are 2.29 Å. All Er(1)-O(4) bond lengths are 2.25 Å. In the second Er site, Er(2) is bonded to one O(2), three equivalent O(3), and three equivalent O(4) atoms to form distorted ErO7 pentagonal bipyramids that share corners with three equivalent Mn(1)O5 trigonal bipyramids and edges with three equivalent Mn(1)O5 trigonal bipyramids. The Er(2)-O(2) bond length is 2.28 Å. All Er(2)-O(3) bond lengths are 2.30 Å. All Er(2)-O(4) bond lengths are 2.25 Å. Mn(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form MnO5 trigonal bipyramids that share  a cornercorner with one Er(2)O7 pentagonal bipyramid, corners with six equivalent Mn(1)O5 trigonal bipyramids, and  an edgeedge with one Er(2)O7 pentagonal bipyramid. The Mn(1)-O(2) bond length is 2.05 Å. The Mn(1)-O(3) bond length is 1.87 Å. The Mn(1)-O(4) bond length is 1.88 Å. Both Mn(1)-O(1) bond lengths are 2.04 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Er(1) and three equivalent Mn(1) atoms to form OErMn3 trigonal pyramids that share corners with six equivalent O(3)Er3Mn tetrahedra, corners with three equivalent O(1)ErMn3 trigonal pyramids, corners with three equivalent O(2)ErMn3 trigonal pyramids, and edges with three equivalent O(4)Er3Mn tetrahedra. In the second O site, O(2) is bonded to one Er(2) and three equivalent Mn(1) atoms to form OErMn3 trigonal pyramids that share corners with six equivalent O(4)Er3Mn tetrahedra, corners with six equivalent O(1)ErMn3 trigonal pyramids, and edges with three equivalent O(3)Er3Mn tetrahedra. In the third O site, O(3) is bonded to one Er(2), two equivalent Er(1), and one Mn(1) atom to form distorted OEr3Mn tetrahedra that share corners with four equivalent O(4)Er3Mn tetrahedra, corners with six equivalent O(3)Er3Mn tetrahedra, corners with four equivalent O(1)ErMn3 trigonal pyramids, edges with three equivalent O(4)Er3Mn tetrahedra, and  an edgeedge with one O(2)ErMn3 trigonal pyramid. In the fourth O site, O(4) is bonded to one Er(2), two equivalent Er(1), and one Mn(1) atom to form OEr3Mn tetrahedra that share corners with four equivalent O(3)Er3Mn tetrahedra, corners with six equivalent O(4)Er3Mn tetrahedra, corners with two equivalent O(2)ErMn3 trigonal pyramids, edges with three equivalent O(3)Er3Mn tetrahedra, and edges with two equivalent O(1)ErMn3 trigonal pyramids.