CaNb2O4 crystallizes in the orthorhombic Pbcm space group. Ca(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form distorted CaO6 pentagonal pyramids that share corners with four equivalent Nb(1)O6 pentagonal pyramids, corners with five equivalent Nb(2)O6 pentagonal pyramids,  an edgeedge with one Nb(2)O6 pentagonal pyramid, edges with two equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Nb(1)O6 pentagonal pyramids, and  a faceface with one Nb(2)O6 pentagonal pyramid. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NbO6 pentagonal pyramids that share corners with four equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Nb(1)O6 pentagonal pyramids, and edges with four equivalent Nb(2)O6 pentagonal pyramids. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form distorted NbO6 pentagonal pyramids that share corners with five equivalent Ca(1)O6 pentagonal pyramids,  an edgeedge with one Ca(1)O6 pentagonal pyramid, edges with two equivalent Nb(2)O6 pentagonal pyramids, edges with four equivalent Nb(1)O6 pentagonal pyramids, and  a faceface with one Ca(1)O6 pentagonal pyramid. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Nb(2), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Nb(2), and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded to two equivalent Ca(1), one Nb(1), and two equivalent Nb(2) atoms to form a mixture of corner, face, and edge-sharing OCa2Nb3 trigonal bipyramids.
CaNb2O4 crystallizes in the orthorhombic Pbcm space group. Ca(1) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form distorted CaO6 pentagonal pyramids that share corners with four equivalent Nb(1)O6 pentagonal pyramids, corners with five equivalent Nb(2)O6 pentagonal pyramids,  an edgeedge with one Nb(2)O6 pentagonal pyramid, edges with two equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Nb(1)O6 pentagonal pyramids, and  a faceface with one Nb(2)O6 pentagonal pyramid. The Ca(1)-O(1) bond length is 2.31 Å. The Ca(1)-O(2) bond length is 2.28 Å. There are two shorter (2.38 Å) and two longer (2.44 Å) Ca(1)-O(3) bond lengths. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted NbO6 pentagonal pyramids that share corners with four equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Ca(1)O6 pentagonal pyramids, edges with two equivalent Nb(1)O6 pentagonal pyramids, and edges with four equivalent Nb(2)O6 pentagonal pyramids. Both Nb(1)-O(1) bond lengths are 2.13 Å. Both Nb(1)-O(2) bond lengths are 2.14 Å. Both Nb(1)-O(3) bond lengths are 2.18 Å. In the second Nb site, Nb(2) is bonded to one O(1), one O(2), and four equivalent O(3) atoms to form distorted NbO6 pentagonal pyramids that share corners with five equivalent Ca(1)O6 pentagonal pyramids,  an edgeedge with one Ca(1)O6 pentagonal pyramid, edges with two equivalent Nb(2)O6 pentagonal pyramids, edges with four equivalent Nb(1)O6 pentagonal pyramids, and  a faceface with one Ca(1)O6 pentagonal pyramid. The Nb(2)-O(1) bond length is 2.13 Å. The Nb(2)-O(2) bond length is 2.13 Å. There are two shorter (2.16 Å) and two longer (2.18 Å) Nb(2)-O(3) bond lengths. There are three inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Nb(2), and two equivalent Nb(1) atoms. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ca(1), one Nb(2), and two equivalent Nb(1) atoms. In the third O site, O(3) is bonded to two equivalent Ca(1), one Nb(1), and two equivalent Nb(2) atoms to form a mixture of corner, face, and edge-sharing OCa2Nb3 trigonal bipyramids.