CaWO2 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(3), and two equivalent O(4) atoms. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(3), one O(4), and three equivalent O(2) atoms. There are two inequivalent W sites. In the first W site, W(1) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(1), and two equivalent O(3) atoms. In the second W site, W(2) is bonded in a distorted pentagonal planar geometry to one O(1), two equivalent O(2), and two equivalent O(4) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ca(1), one W(2), and two equivalent W(1) atoms. In the second O site, O(2) is bonded to three equivalent Ca(2), one W(1), and two equivalent W(2) atoms to form OCa3W3 octahedra that share  a cornercorner with one O(3)Ca3W2 trigonal bipyramid, corners with four equivalent O(4)Ca3W2 trigonal bipyramids, edges with four equivalent O(2)Ca3W3 octahedra, edges with two equivalent O(3)Ca3W2 trigonal bipyramids, and  a faceface with one O(4)Ca3W2 trigonal bipyramid. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent W(1) atoms to form distorted OCa3W2 trigonal bipyramids that share  a cornercorner with one O(2)Ca3W3 octahedra, corners with three equivalent O(4)Ca3W2 trigonal bipyramids, edges with two equivalent O(2)Ca3W3 octahedra,  an edgeedge with one O(4)Ca3W2 trigonal bipyramid, and edges with two equivalent O(3)Ca3W2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 19°. In the fourth O site, O(4) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent W(2) atoms to form distorted OCa3W2 trigonal bipyramids that share corners with four equivalent O(2)Ca3W3 octahedra, corners with three equivalent O(3)Ca3W2 trigonal bipyramids,  an edgeedge with one O(3)Ca3W2 trigonal bipyramid, edges with two equivalent O(4)Ca3W2 trigonal bipyramids, and  a faceface with one O(2)Ca3W3 octahedra. The corner-sharing octahedral tilt angles range from 43-54°.
CaWO2 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(1), two equivalent O(3), and two equivalent O(4) atoms. The Ca(1)-O(1) bond length is 2.33 Å. Both Ca(1)-O(3) bond lengths are 2.31 Å. There is one shorter (2.31 Å) and one longer (2.32 Å) Ca(1)-O(4) bond length. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(3), one O(4), and three equivalent O(2) atoms. The Ca(2)-O(3) bond length is 2.29 Å. The Ca(2)-O(4) bond length is 2.20 Å. There are a spread of Ca(2)-O(2) bond distances ranging from 2.33-2.54 Å. There are two inequivalent W sites. In the first W site, W(1) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(1), and two equivalent O(3) atoms. The W(1)-O(2) bond length is 2.25 Å. There is one shorter (2.18 Å) and one longer (2.22 Å) W(1)-O(1) bond length. There is one shorter (2.22 Å) and one longer (2.28 Å) W(1)-O(3) bond length. In the second W site, W(2) is bonded in a distorted pentagonal planar geometry to one O(1), two equivalent O(2), and two equivalent O(4) atoms. The W(2)-O(1) bond length is 2.10 Å. There is one shorter (2.22 Å) and one longer (2.32 Å) W(2)-O(2) bond length. There is one shorter (2.21 Å) and one longer (2.24 Å) W(2)-O(4) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded in a rectangular see-saw-like geometry to one Ca(1), one W(2), and two equivalent W(1) atoms. In the second O site, O(2) is bonded to three equivalent Ca(2), one W(1), and two equivalent W(2) atoms to form OCa3W3 octahedra that share  a cornercorner with one O(3)Ca3W2 trigonal bipyramid, corners with four equivalent O(4)Ca3W2 trigonal bipyramids, edges with four equivalent O(2)Ca3W3 octahedra, edges with two equivalent O(3)Ca3W2 trigonal bipyramids, and  a faceface with one O(4)Ca3W2 trigonal bipyramid. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent W(1) atoms to form distorted OCa3W2 trigonal bipyramids that share  a cornercorner with one O(2)Ca3W3 octahedra, corners with three equivalent O(4)Ca3W2 trigonal bipyramids, edges with two equivalent O(2)Ca3W3 octahedra,  an edgeedge with one O(4)Ca3W2 trigonal bipyramid, and edges with two equivalent O(3)Ca3W2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 19°. In the fourth O site, O(4) is bonded to one Ca(2), two equivalent Ca(1), and two equivalent W(2) atoms to form distorted OCa3W2 trigonal bipyramids that share corners with four equivalent O(2)Ca3W3 octahedra, corners with three equivalent O(3)Ca3W2 trigonal bipyramids,  an edgeedge with one O(3)Ca3W2 trigonal bipyramid, edges with two equivalent O(4)Ca3W2 trigonal bipyramids, and  a faceface with one O(2)Ca3W3 octahedra. The corner-sharing octahedral tilt angles range from 43-54°.