CaMn4O9 crystallizes in the tetragonal P4/n space group. Ca(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Mn(1) is bonded to one O(1), one O(2), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing MnO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted square co-planar geometry to four equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Mn(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Mn(1) atoms.
CaMn4O9 crystallizes in the tetragonal P4/n space group. Ca(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. All Ca(1)-O(2) bond lengths are 2.34 Å. All Ca(1)-O(3) bond lengths are 2.67 Å. Mn(1) is bonded to one O(1), one O(2), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing MnO5 trigonal bipyramids. The Mn(1)-O(1) bond length is 2.08 Å. The Mn(1)-O(2) bond length is 1.71 Å. There are a spread of Mn(1)-O(3) bond distances ranging from 1.92-2.01 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted square co-planar geometry to four equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Mn(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Mn(1) atoms.