CaMo4O9 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. Mo(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 MoO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mo(1) atoms to form a mixture of distorted corner and edge-sharing OMo4 trigonal pyramids. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Mo(1) atom. In the third O site, O(3) is bonded to one Ca(1) and three equivalent Mo(1) atoms to form distorted OCaMo3 tetrahedra that share corners with three equivalent O(3)CaMo3 tetrahedra,  a cornercorner with one O(1)Mo4 trigonal pyramid, edges with three equivalent O(3)CaMo3 tetrahedra, and  an edgeedge with one O(1)Mo4 trigonal pyramid.
CaMo4O9 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 2.40 Å. All Ca(1)-O(3) bond lengths are 2.55 Å. Mo(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 MoO5 trigonal bipyramids. The Mo(1)-O(1) bond length is 2.19 Å. The Mo(1)-O(2) bond length is 1.81 Å. There are a spread of Mo(1)-O(3) bond distances ranging from 2.06-2.22 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Mo(1) atoms to form a mixture of distorted corner and edge-sharing OMo4 trigonal pyramids. In the second O site, O(2) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Mo(1) atom. In the third O site, O(3) is bonded to one Ca(1) and three equivalent Mo(1) atoms to form distorted OCaMo3 tetrahedra that share corners with three equivalent O(3)CaMo3 tetrahedra,  a cornercorner with one O(1)Mo4 trigonal pyramid, edges with three equivalent O(3)CaMo3 tetrahedra, and  an edgeedge with one O(1)Mo4 trigonal pyramid.