CaCr4O9 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. Cr(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 CrO5 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 Cr(1) atoms. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Cr(1) atoms.
CaCr4O9 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 2.38 Å. All Ca(1)-O(3) bond lengths are 2.61 Å. Cr(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 CrO5 trigonal bipyramids. The Cr(1)-O(1) bond length is 2.03 Å. The Cr(1)-O(2) bond length is 1.68 Å. There are a spread of Cr(1)-O(3) bond distances ranging from 1.93-2.01 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 Cr(1) atoms. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Cr(1) atoms.