Mn4Ta2O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted TaO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with six equivalent Mn(1)O6 octahedra, edges with three equivalent Mn(2)O6 octahedra, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to six equivalent O(2) atoms to form MnO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with six equivalent Ta(1)O6 octahedra, edges with three equivalent Mn(1)O6 octahedra, and  a faceface with one Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. In the second Mn site, Mn(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Mn(1)O6 octahedra, corners with three equivalent Mn(2)O6 octahedra, edges with three equivalent Ta(1)O6 octahedra, and  a faceface with one Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-69°. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ta(1) and two equivalent Mn(2) atoms to form distorted OTa2Mn2 trigonal pyramids that share corners with four equivalent O(1)Ta2Mn2 trigonal pyramids, corners with eight equivalent O(2)TaMn3 trigonal pyramids, edges with two equivalent O(1)Ta2Mn2 trigonal pyramids, and edges with two equivalent O(2)TaMn3 trigonal pyramids. In the second O site, O(2) is bonded to one Ta(1), one Mn(2), and two equivalent Mn(1) atoms to form distorted OTaMn3 trigonal pyramids that share corners with four equivalent O(1)Ta2Mn2 trigonal pyramids, corners with eight equivalent O(2)TaMn3 trigonal pyramids,  an edgeedge with one O(1)Ta2Mn2 trigonal pyramid, and edges with three equivalent O(2)TaMn3 trigonal pyramids.
Mn4Ta2O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. Ta(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted TaO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with six equivalent Mn(1)O6 octahedra, edges with three equivalent Mn(2)O6 octahedra, and  a faceface with one Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. All Ta(1)-O(1) bond lengths are 2.13 Å. All Ta(1)-O(2) bond lengths are 1.91 Å. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to six equivalent O(2) atoms to form MnO6 octahedra that share corners with three equivalent Mn(2)O6 octahedra, corners with six equivalent Ta(1)O6 octahedra, edges with three equivalent Mn(1)O6 octahedra, and  a faceface with one Mn(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. There are three shorter (2.13 Å) and three longer (2.24 Å) Mn(1)-O(2) bond lengths. In the second Mn site, Mn(2) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form distorted MnO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Mn(1)O6 octahedra, corners with three equivalent Mn(2)O6 octahedra, edges with three equivalent Ta(1)O6 octahedra, and  a faceface with one Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 49-69°. All Mn(2)-O(1) bond lengths are 2.07 Å. All Mn(2)-O(2) bond lengths are 2.32 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ta(1) and two equivalent Mn(2) atoms to form distorted OTa2Mn2 trigonal pyramids that share corners with four equivalent O(1)Ta2Mn2 trigonal pyramids, corners with eight equivalent O(2)TaMn3 trigonal pyramids, edges with two equivalent O(1)Ta2Mn2 trigonal pyramids, and edges with two equivalent O(2)TaMn3 trigonal pyramids. In the second O site, O(2) is bonded to one Ta(1), one Mn(2), and two equivalent Mn(1) atoms to form distorted OTaMn3 trigonal pyramids that share corners with four equivalent O(1)Ta2Mn2 trigonal pyramids, corners with eight equivalent O(2)TaMn3 trigonal pyramids,  an edgeedge with one O(1)Ta2Mn2 trigonal pyramid, and edges with three equivalent O(2)TaMn3 trigonal pyramids.