Ca2V2O9 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 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(8), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(2), one O(5), one O(6), one O(7), one O(9), and two equivalent O(4) atoms. There are two inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing VO4 tetrahedra. In the second V site, V(2) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form corner-sharing VO4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one V(1) and one V(2) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(2), and one V(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ca(1) and one V(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one V(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Ca(2), and one V(2) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ca(1), one Ca(2), and one V(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one V(2) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Ca(1) and one O(9) atom. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Ca(2) and one O(8) atom.
Ca2V2O9 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 8-coordinate geometry to one O(2), one O(3), one O(4), one O(5), one O(6), one O(8), and two equivalent O(7) atoms. The Ca(1)-O(2) bond length is 2.34 Å. The Ca(1)-O(3) bond length is 2.33 Å. The Ca(1)-O(4) bond length is 2.83 Å. The Ca(1)-O(5) bond length is 2.34 Å. The Ca(1)-O(6) bond length is 2.57 Å. The Ca(1)-O(8) bond length is 3.04 Å. There is one shorter (2.39 Å) and one longer (2.49 Å) Ca(1)-O(7) bond length. In the second Ca site, Ca(2) is bonded in a 7-coordinate geometry to one O(2), one O(5), one O(6), one O(7), one O(9), and two equivalent O(4) atoms. The Ca(2)-O(2) bond length is 2.33 Å. The Ca(2)-O(5) bond length is 2.41 Å. The Ca(2)-O(6) bond length is 2.36 Å. The Ca(2)-O(7) bond length is 2.58 Å. The Ca(2)-O(9) bond length is 3.00 Å. There is one shorter (2.35 Å) and one longer (2.42 Å) Ca(2)-O(4) bond length. There are two inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form corner-sharing VO4 tetrahedra. The V(1)-O(1) bond length is 1.82 Å. The V(1)-O(2) bond length is 1.74 Å. The V(1)-O(3) bond length is 1.68 Å. The V(1)-O(4) bond length is 1.75 Å. In the second V site, V(2) is bonded to one O(1), one O(5), one O(6), and one O(7) atom to form corner-sharing VO4 tetrahedra. The V(2)-O(1) bond length is 1.80 Å. The V(2)-O(5) bond length is 1.71 Å. The V(2)-O(6) bond length is 1.71 Å. The V(2)-O(7) bond length is 1.74 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one V(1) and one V(2) atom. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(2), and one V(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ca(1) and one V(1) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(1), two equivalent Ca(2), and one V(1) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Ca(1), one Ca(2), and one V(2) atom. In the sixth O site, O(6) is bonded in a distorted T-shaped geometry to one Ca(1), one Ca(2), and one V(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one V(2) atom. In the eighth O site, O(8) is bonded in a bent 120 degrees geometry to one Ca(1) and one O(9) atom. The O(8)-O(9) bond length is 1.23 Å. In the ninth O site, O(9) is bonded in a distorted bent 120 degrees geometry to one Ca(2) and one O(8) atom.