CaCr2O7 crystallizes in the monoclinic P2_1 space group. Ca(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form CaO5 trigonal bipyramids that share corners with two equivalent Cr(2)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, and corners with two equivalent Ca(1)O5 trigonal bipyramids. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(2)O4 tetrahedra and corners with three equivalent Ca(1)O5 trigonal bipyramids. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(1)O4 tetrahedra and corners with two equivalent Ca(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Cr(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Cr(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Ca(1) and one Cr(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one Cr(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Cr(1) and one Cr(2) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Cr(1) atom.
CaCr2O7 crystallizes in the monoclinic P2_1 space group. Ca(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form CaO5 trigonal bipyramids that share corners with two equivalent Cr(2)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, and corners with two equivalent Ca(1)O5 trigonal bipyramids. The Ca(1)-O(3) bond length is 2.33 Å. The Ca(1)-O(4) bond length is 2.34 Å. The Ca(1)-O(5) bond length is 2.30 Å. There is one shorter (2.40 Å) and one longer (2.52 Å) Ca(1)-O(2) bond length. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(2)O4 tetrahedra and corners with three equivalent Ca(1)O5 trigonal bipyramids. The Cr(1)-O(2) bond length is 1.69 Å. The Cr(1)-O(4) bond length is 1.65 Å. The Cr(1)-O(6) bond length is 1.76 Å. The Cr(1)-O(7) bond length is 1.59 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(1)O4 tetrahedra and corners with two equivalent Ca(1)O5 trigonal bipyramids. The Cr(2)-O(1) bond length is 1.60 Å. The Cr(2)-O(3) bond length is 1.65 Å. The Cr(2)-O(5) bond length is 1.65 Å. The Cr(2)-O(6) bond length is 1.81 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Cr(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Ca(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Cr(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Ca(1) and one Cr(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Ca(1) and one Cr(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Cr(1) and one Cr(2) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Cr(1) atom.