Y2Cr3O9 crystallizes in the tetragonal P4/mmm space group. Y(1) is bonded to four equivalent O(1), four equivalent O(3), and four equivalent O(4) atoms to form distorted YO12 cuboctahedra that share corners with eight equivalent Y(1)O12 cuboctahedra, faces with five equivalent Y(1)O12 cuboctahedra, faces with four equivalent Cr(1)O6 octahedra, and faces with four equivalent Cr(2)O6 octahedra. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CrO6 octahedra that share corners with two Cr(2,2)O6 octahedra; corners with four equivalent Cr(1)O6 octahedra; and faces with eight equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form distorted CrO6 octahedra that share  a cornercorner with one Cr(1)O6 octahedra; corners with five Cr(2,2)O6 octahedra; and faces with four equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-23°. In the third Cr site, Cr(2) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form distorted CrO6 octahedra that share  a cornercorner with one Cr(1)O6 octahedra; corners with five Cr(2,2)O6 octahedra; and faces with four equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-23°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Y(1), one Cr(1), and one Cr(2) atom. In the second O site, O(2) is bonded in a linear geometry to two Cr(2,2) atoms. In the third O site, O(3) is bonded in a linear geometry to four equivalent Y(1) and two equivalent Cr(1) atoms. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to two equivalent Y(1) and two equivalent Cr(2) atoms.
Y2Cr3O9 crystallizes in the tetragonal P4/mmm space group. Y(1) is bonded to four equivalent O(1), four equivalent O(3), and four equivalent O(4) atoms to form distorted YO12 cuboctahedra that share corners with eight equivalent Y(1)O12 cuboctahedra, faces with five equivalent Y(1)O12 cuboctahedra, faces with four equivalent Cr(1)O6 octahedra, and faces with four equivalent Cr(2)O6 octahedra. All Y(1)-O(1) bond lengths are 2.68 Å. All Y(1)-O(3) bond lengths are 2.88 Å. All Y(1)-O(4) bond lengths are 2.38 Å. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form CrO6 octahedra that share corners with two Cr(2,2)O6 octahedra; corners with four equivalent Cr(1)O6 octahedra; and faces with eight equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedra are not tilted. Both Cr(1)-O(1) bond lengths are 1.93 Å. All Cr(1)-O(3) bond lengths are 1.89 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form distorted CrO6 octahedra that share  a cornercorner with one Cr(1)O6 octahedra; corners with five Cr(2,2)O6 octahedra; and faces with four equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-23°. The Cr(2)-O(1) bond length is 2.08 Å. The Cr(2)-O(2) bond length is 1.76 Å. All Cr(2)-O(4) bond lengths are 1.93 Å. In the third Cr site, Cr(2) is bonded to one O(1), one O(2), and four equivalent O(4) atoms to form distorted CrO6 octahedra that share  a cornercorner with one Cr(1)O6 octahedra; corners with five Cr(2,2)O6 octahedra; and faces with four equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-23°. The Cr(2)-O(1) bond length is 2.08 Å. The Cr(2)-O(2) bond length is 1.76 Å. All Cr(2)-O(4) bond lengths are 1.93 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Y(1), one Cr(1), and one Cr(2) atom. In the second O site, O(2) is bonded in a linear geometry to two Cr(2,2) atoms. In the third O site, O(3) is bonded in a linear geometry to four equivalent Y(1) and two equivalent Cr(1) atoms. In the fourth O site, O(4) is bonded in a distorted see-saw-like geometry to two equivalent Y(1) and two equivalent Cr(2) atoms.