Y2Cr2O7 crystallizes in the triclinic P-1 space group. There are four inequivalent Y sites. In the first Y site, Y(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(5), and two equivalent O(7) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, edges with two equivalent Y(4)O8 hexagonal bipyramids, edges with two equivalent Cr(2)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the second Y site, Y(2) is bonded to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, edges with two equivalent Y(4)O8 hexagonal bipyramids, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the third Y site, Y(3) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(4)O8 hexagonal bipyramids, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. In the fourth Y site, Y(4) is bonded to two equivalent O(1), two equivalent O(3), two equivalent O(6), and two equivalent O(7) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(3)O6 octahedra. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form CrO6 octahedra that share corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, and edges with two equivalent Y(4)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 48°. In the second Cr site, Cr(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, and edges with two equivalent Y(4)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. In the third Cr site, Cr(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, and edges with two equivalent Y(4)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. In the fourth Cr site, Cr(4) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, and edges with two equivalent Y(3)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Y(1), one Y(2), one Y(3), and one Y(4) atom to form OY4 tetrahedra that share corners with two equivalent O(4)Y2Cr2 tetrahedra, corners with two equivalent O(5)Y2Cr2 tetrahedra, corners with two equivalent O(7)Y2Cr2 tetrahedra, corners with four equivalent O(1)Y4 tetrahedra,  an edgeedge with one O(4)Y2Cr2 tetrahedra,  an edgeedge with one O(5)Y2Cr2 tetrahedra, and  an edgeedge with one O(7)Y2Cr2 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Y(1), one Y(3), one Cr(2), and one Cr(4) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Y(2), one Y(4), one Cr(1), and one Cr(3) atom. In the fourth O site, O(4) is bonded to one Y(2), one Y(3), one Cr(1), and one Cr(4) atom to form distorted OY2Cr2 tetrahedra that share corners with two equivalent O(5)Y2Cr2 tetrahedra, corners with two equivalent O(1)Y4 tetrahedra, corners with four equivalent O(4)Y2Cr2 tetrahedra,  an edgeedge with one O(5)Y2Cr2 tetrahedra, and  an edgeedge with one O(1)Y4 tetrahedra. In the fifth O site, O(5) is bonded to one Y(1), one Y(2), one Cr(3), and one Cr(4) atom to form distorted OY2Cr2 tetrahedra that share corners with two equivalent O(4)Y2Cr2 tetrahedra, corners with two equivalent O(7)Y2Cr2 tetrahedra, corners with two equivalent O(1)Y4 tetrahedra, corners with four equivalent O(5)Y2Cr2 tetrahedra,  an edgeedge with one O(4)Y2Cr2 tetrahedra,  an edgeedge with one O(7)Y2Cr2 tetrahedra, and  an edgeedge with one O(1)Y4 tetrahedra. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Y(3), one Y(4), one Cr(1), and one Cr(2) atom. In the seventh O site, O(7) is bonded to one Y(1), one Y(4), one Cr(2), and one Cr(3) atom to form distorted OY2Cr2 tetrahedra that share corners with two equivalent O(5)Y2Cr2 tetrahedra, corners with two equivalent O(1)Y4 tetrahedra, corners with four equivalent O(7)Y2Cr2 tetrahedra,  an edgeedge with one O(5)Y2Cr2 tetrahedra, and  an edgeedge with one O(1)Y4 tetrahedra.
Y2Cr2O7 crystallizes in the triclinic P-1 space group. There are four inequivalent Y sites. In the first Y site, Y(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(5), and two equivalent O(7) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, edges with two equivalent Y(4)O8 hexagonal bipyramids, edges with two equivalent Cr(2)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. Both Y(1)-O(1) bond lengths are 2.19 Å. Both Y(1)-O(2) bond lengths are 2.46 Å. Both Y(1)-O(5) bond lengths are 2.50 Å. Both Y(1)-O(7) bond lengths are 2.48 Å. In the second Y site, Y(2) is bonded to two equivalent O(1), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, edges with two equivalent Y(4)O8 hexagonal bipyramids, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(3)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. Both Y(2)-O(1) bond lengths are 2.18 Å. Both Y(2)-O(3) bond lengths are 2.50 Å. Both Y(2)-O(4) bond lengths are 2.51 Å. Both Y(2)-O(5) bond lengths are 2.44 Å. In the third Y site, Y(3) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(4)O8 hexagonal bipyramids, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(4)O6 octahedra. Both Y(3)-O(1) bond lengths are 2.18 Å. Both Y(3)-O(2) bond lengths are 2.52 Å. Both Y(3)-O(4) bond lengths are 2.46 Å. Both Y(3)-O(6) bond lengths are 2.47 Å. In the fourth Y site, Y(4) is bonded to two equivalent O(1), two equivalent O(3), two equivalent O(6), and two equivalent O(7) atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(2)O6 octahedra, and edges with two equivalent Cr(3)O6 octahedra. Both Y(4)-O(1) bond lengths are 2.19 Å. Both Y(4)-O(3) bond lengths are 2.47 Å. Both Y(4)-O(6) bond lengths are 2.50 Å. Both Y(4)-O(7) bond lengths are 2.46 Å. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(3), two equivalent O(4), and two equivalent O(6) atoms to form CrO6 octahedra that share corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, edges with two equivalent Y(2)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, and edges with two equivalent Y(4)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 48°. Both Cr(1)-O(3) bond lengths are 1.91 Å. Both Cr(1)-O(4) bond lengths are 1.95 Å. Both Cr(1)-O(6) bond lengths are 1.99 Å. In the second Cr site, Cr(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(3)O8 hexagonal bipyramids, and edges with two equivalent Y(4)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. Both Cr(2)-O(2) bond lengths are 1.96 Å. Both Cr(2)-O(6) bond lengths are 1.91 Å. Both Cr(2)-O(7) bond lengths are 1.99 Å. In the third Cr site, Cr(3) is bonded to two equivalent O(3), two equivalent O(5), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, and edges with two equivalent Y(4)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. Both Cr(3)-O(3) bond lengths are 1.99 Å. Both Cr(3)-O(5) bond lengths are 1.93 Å. Both Cr(3)-O(7) bond lengths are 1.94 Å. In the fourth Cr site, Cr(4) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(2)O6 octahedra, corners with two equivalent Cr(3)O6 octahedra, edges with two equivalent Y(1)O8 hexagonal bipyramids, edges with two equivalent Y(2)O8 hexagonal bipyramids, and edges with two equivalent Y(3)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-49°. Both Cr(4)-O(2) bond lengths are 1.93 Å. Both Cr(4)-O(4) bond lengths are 1.94 Å. Both Cr(4)-O(5) bond lengths are 1.99 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Y(1), one Y(2), one Y(3), and one Y(4) atom to form OY4 tetrahedra that share corners with two equivalent O(4)Y2Cr2 tetrahedra, corners with two equivalent O(5)Y2Cr2 tetrahedra, corners with two equivalent O(7)Y2Cr2 tetrahedra, corners with four equivalent O(1)Y4 tetrahedra,  an edgeedge with one O(4)Y2Cr2 tetrahedra,  an edgeedge with one O(5)Y2Cr2 tetrahedra, and  an edgeedge with one O(7)Y2Cr2 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Y(1), one Y(3), one Cr(2), and one Cr(4) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Y(2), one Y(4), one Cr(1), and one Cr(3) atom. In the fourth O site, O(4) is bonded to one Y(2), one Y(3), one Cr(1), and one Cr(4) atom to form distorted OY2Cr2 tetrahedra that share corners with two equivalent O(5)Y2Cr2 tetrahedra, corners with two equivalent O(1)Y4 tetrahedra, corners with four equivalent O(4)Y2Cr2 tetrahedra,  an edgeedge with one O(5)Y2Cr2 tetrahedra, and  an edgeedge with one O(1)Y4 tetrahedra. In the fifth O site, O(5) is bonded to one Y(1), one Y(2), one Cr(3), and one Cr(4) atom to form distorted OY2Cr2 tetrahedra that share corners with two equivalent O(4)Y2Cr2 tetrahedra, corners with two equivalent O(7)Y2Cr2 tetrahedra, corners with two equivalent O(1)Y4 tetrahedra, corners with four equivalent O(5)Y2Cr2 tetrahedra,  an edgeedge with one O(4)Y2Cr2 tetrahedra,  an edgeedge with one O(7)Y2Cr2 tetrahedra, and  an edgeedge with one O(1)Y4 tetrahedra. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Y(3), one Y(4), one Cr(1), and one Cr(2) atom. In the seventh O site, O(7) is bonded to one Y(1), one Y(4), one Cr(2), and one Cr(3) atom to form distorted OY2Cr2 tetrahedra that share corners with two equivalent O(5)Y2Cr2 tetrahedra, corners with two equivalent O(1)Y4 tetrahedra, corners with four equivalent O(7)Y2Cr2 tetrahedra,  an edgeedge with one O(5)Y2Cr2 tetrahedra, and  an edgeedge with one O(1)Y4 tetrahedra.