CaV4O8 crystallizes in the monoclinic Cm space group. Ca(1) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(6), and two equivalent O(7) atoms. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 50-52°. In the second V site, V(2) is bonded to one O(4), one O(8), two equivalent O(3), and two equivalent O(6) atoms to form a mixture of distorted edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 50-55°. In the third V site, V(3) is bonded to one O(1), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles are 52°. In the fourth V site, V(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one V(3) and two equivalent V(4) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one V(1) and two equivalent V(3) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one V(4) and two equivalent V(2) atoms. In the fourth O site, O(4) is bonded to one Ca(1), one V(2), and two equivalent V(1) atoms to form distorted OCaV3 trigonal pyramids that share corners with two equivalent O(4)CaV3 trigonal pyramids, edges with two equivalent O(7)Ca2V3 square pyramids, and edges with two equivalent O(6)Ca2V3 trigonal bipyramids. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one V(4) and two equivalent V(1) atoms. In the sixth O site, O(6) is bonded to two equivalent Ca(1), one V(3), and two equivalent V(2) atoms to form distorted OCa2V3 trigonal bipyramids that share corners with two equivalent O(7)Ca2V3 square pyramids,  an edgeedge with one O(7)Ca2V3 square pyramid, edges with two equivalent O(6)Ca2V3 trigonal bipyramids, and edges with two equivalent O(4)CaV3 trigonal pyramids. In the seventh O site, O(7) is bonded to two equivalent Ca(1), one V(1), and two equivalent V(4) atoms to form OCa2V3 square pyramids that share corners with two equivalent O(6)Ca2V3 trigonal bipyramids, edges with two equivalent O(7)Ca2V3 square pyramids,  an edgeedge with one O(6)Ca2V3 trigonal bipyramid, and edges with two equivalent O(4)CaV3 trigonal pyramids. In the eighth O site, O(8) is bonded in a trigonal non-coplanar geometry to one V(2) and two equivalent V(3) atoms.
CaV4O8 crystallizes in the monoclinic Cm space group. Ca(1) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(6), and two equivalent O(7) atoms. The Ca(1)-O(4) bond length is 2.45 Å. Both Ca(1)-O(6) bond lengths are 2.31 Å. Both Ca(1)-O(7) bond lengths are 2.31 Å. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(2), one O(7), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 50-52°. The V(1)-O(2) bond length is 1.82 Å. The V(1)-O(7) bond length is 2.06 Å. Both V(1)-O(4) bond lengths are 2.05 Å. Both V(1)-O(5) bond lengths are 1.98 Å. In the second V site, V(2) is bonded to one O(4), one O(8), two equivalent O(3), and two equivalent O(6) atoms to form a mixture of distorted edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 50-55°. The V(2)-O(4) bond length is 1.95 Å. The V(2)-O(8) bond length is 1.82 Å. Both V(2)-O(3) bond lengths are 1.94 Å. Both V(2)-O(6) bond lengths are 2.17 Å. In the third V site, V(3) is bonded to one O(1), one O(6), two equivalent O(2), and two equivalent O(8) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles are 52°. The V(3)-O(1) bond length is 1.90 Å. The V(3)-O(6) bond length is 2.06 Å. Both V(3)-O(2) bond lengths are 2.06 Å. Both V(3)-O(8) bond lengths are 2.07 Å. In the fourth V site, V(4) is bonded to one O(3), one O(5), two equivalent O(1), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. The V(4)-O(3) bond length is 2.01 Å. The V(4)-O(5) bond length is 1.99 Å. Both V(4)-O(1) bond lengths are 1.97 Å. Both V(4)-O(7) bond lengths are 2.20 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal planar geometry to one V(3) and two equivalent V(4) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one V(1) and two equivalent V(3) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one V(4) and two equivalent V(2) atoms. In the fourth O site, O(4) is bonded to one Ca(1), one V(2), and two equivalent V(1) atoms to form distorted OCaV3 trigonal pyramids that share corners with two equivalent O(4)CaV3 trigonal pyramids, edges with two equivalent O(7)Ca2V3 square pyramids, and edges with two equivalent O(6)Ca2V3 trigonal bipyramids. In the fifth O site, O(5) is bonded in a trigonal non-coplanar geometry to one V(4) and two equivalent V(1) atoms. In the sixth O site, O(6) is bonded to two equivalent Ca(1), one V(3), and two equivalent V(2) atoms to form distorted OCa2V3 trigonal bipyramids that share corners with two equivalent O(7)Ca2V3 square pyramids,  an edgeedge with one O(7)Ca2V3 square pyramid, edges with two equivalent O(6)Ca2V3 trigonal bipyramids, and edges with two equivalent O(4)CaV3 trigonal pyramids. In the seventh O site, O(7) is bonded to two equivalent Ca(1), one V(1), and two equivalent V(4) atoms to form OCa2V3 square pyramids that share corners with two equivalent O(6)Ca2V3 trigonal bipyramids, edges with two equivalent O(7)Ca2V3 square pyramids,  an edgeedge with one O(6)Ca2V3 trigonal bipyramid, and edges with two equivalent O(4)CaV3 trigonal pyramids. In the eighth O site, O(8) is bonded in a trigonal non-coplanar geometry to one V(2) and two equivalent V(3) atoms.