NaCr6O11 crystallizes in the monoclinic Cc space group. Na(1) is bonded to one O(10), one O(11), one O(2), one O(3), one O(7), one O(8), two equivalent O(1), two equivalent O(6), and two equivalent O(9) atoms to form distorted NaO12 cuboctahedra that share corners with six equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(5)O6 octahedra, edges with two equivalent Cr(6)O6 octahedra, edges with three equivalent Cr(2)O5 trigonal bipyramids, faces with three equivalent Cr(3)O6 octahedra, and faces with three equivalent Cr(4)O6 octahedra. There are six inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form CrO6 octahedra that share corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with two equivalent Cr(2)O5 trigonal bipyramids, edges with two equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(5)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the second Cr site, Cr(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(9) atom to form CrO5 trigonal bipyramids that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, corners with three equivalent Cr(4)O6 octahedra, and edges with three equivalent Na(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 41-56°. In the third Cr site, Cr(3) is bonded to one O(1), one O(10), one O(3), one O(6), one O(8), and one O(9) atom to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Cr(2)O5 trigonal bipyramids, faces with three equivalent Na(1)O12 cuboctahedra, and  a faceface with one Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the fourth Cr site, Cr(4) is bonded to one O(1), one O(11), one O(2), one O(6), one O(7), and one O(9) atom to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Cr(2)O5 trigonal bipyramids, faces with three equivalent Na(1)O12 cuboctahedra, and  a faceface with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the fifth Cr site, Cr(5) is bonded to one O(10), one O(11), one O(3), one O(4), one O(5), and one O(7) atom to form CrO6 octahedra that share corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with two equivalent Cr(2)O5 trigonal bipyramids, edges with two equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. In the sixth Cr site, Cr(6) is bonded to one O(10), one O(11), one O(2), one O(4), one O(5), and one O(8) atom to form CrO6 octahedra that share corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with two equivalent Cr(2)O5 trigonal bipyramids, edges with two equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. There are eleven inequivalent O sites. In the first O site, O(5) is bonded in a rectangular see-saw-like geometry to one Cr(1), one Cr(2), one Cr(5), and one Cr(6) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Cr(2), one Cr(3), and one Cr(4) atom. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Na(1), one Cr(1), one Cr(4), and one Cr(5) atom. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), one Cr(3), and one Cr(6) atom. In the fifth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Cr(2), one Cr(3), and one Cr(4) atom. In the sixth O site, O(10) is bonded in a 3-coordinate geometry to one Na(1), one Cr(3), one Cr(5), and one Cr(6) atom. In the seventh O site, O(11) is bonded in a 4-coordinate geometry to one Na(1), one Cr(4), one Cr(5), and one Cr(6) atom. In the eighth O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Cr(2), one Cr(3), and one Cr(4) atom. In the ninth O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Cr(1), one Cr(4), and one Cr(6) atom. In the tenth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Cr(1), one Cr(3), and one Cr(5) atom. In the eleventh O site, O(4) is bonded in a rectangular see-saw-like geometry to one Cr(1), one Cr(2), one Cr(5), and one Cr(6) atom.
NaCr6O11 crystallizes in the monoclinic Cc space group. Na(1) is bonded to one O(10), one O(11), one O(2), one O(3), one O(7), one O(8), two equivalent O(1), two equivalent O(6), and two equivalent O(9) atoms to form distorted NaO12 cuboctahedra that share corners with six equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(1)O6 octahedra, edges with two equivalent Cr(5)O6 octahedra, edges with two equivalent Cr(6)O6 octahedra, edges with three equivalent Cr(2)O5 trigonal bipyramids, faces with three equivalent Cr(3)O6 octahedra, and faces with three equivalent Cr(4)O6 octahedra. The Na(1)-O(10) bond length is 2.80 Å. The Na(1)-O(11) bond length is 2.72 Å. The Na(1)-O(2) bond length is 2.71 Å. The Na(1)-O(3) bond length is 2.78 Å. The Na(1)-O(7) bond length is 2.70 Å. The Na(1)-O(8) bond length is 2.79 Å. There is one shorter (2.91 Å) and one longer (2.92 Å) Na(1)-O(1) bond length. There is one shorter (2.91 Å) and one longer (2.92 Å) Na(1)-O(6) bond length. Both Na(1)-O(9) bond lengths are 2.92 Å. There are six inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form CrO6 octahedra that share corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with two equivalent Cr(2)O5 trigonal bipyramids, edges with two equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(5)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. The Cr(1)-O(2) bond length is 1.93 Å. The Cr(1)-O(3) bond length is 1.93 Å. The Cr(1)-O(4) bond length is 2.03 Å. The Cr(1)-O(5) bond length is 2.03 Å. The Cr(1)-O(7) bond length is 1.93 Å. The Cr(1)-O(8) bond length is 1.92 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(4), one O(5), one O(6), and one O(9) atom to form CrO5 trigonal bipyramids that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Cr(3)O6 octahedra, corners with three equivalent Cr(4)O6 octahedra, and edges with three equivalent Na(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 41-56°. The Cr(2)-O(1) bond length is 1.82 Å. The Cr(2)-O(4) bond length is 2.12 Å. The Cr(2)-O(5) bond length is 2.11 Å. The Cr(2)-O(6) bond length is 1.82 Å. The Cr(2)-O(9) bond length is 1.82 Å. In the third Cr site, Cr(3) is bonded to one O(1), one O(10), one O(3), one O(6), one O(8), and one O(9) atom to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Cr(2)O5 trigonal bipyramids, faces with three equivalent Na(1)O12 cuboctahedra, and  a faceface with one Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. The Cr(3)-O(1) bond length is 2.06 Å. The Cr(3)-O(10) bond length is 1.96 Å. The Cr(3)-O(3) bond length is 1.97 Å. The Cr(3)-O(6) bond length is 2.06 Å. The Cr(3)-O(8) bond length is 1.96 Å. The Cr(3)-O(9) bond length is 2.06 Å. In the fourth Cr site, Cr(4) is bonded to one O(1), one O(11), one O(2), one O(6), one O(7), and one O(9) atom to form CrO6 octahedra that share corners with two equivalent Cr(1)O6 octahedra, corners with two equivalent Cr(5)O6 octahedra, corners with two equivalent Cr(6)O6 octahedra, corners with three equivalent Cr(2)O5 trigonal bipyramids, faces with three equivalent Na(1)O12 cuboctahedra, and  a faceface with one Cr(3)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. The Cr(4)-O(1) bond length is 2.06 Å. The Cr(4)-O(11) bond length is 1.97 Å. The Cr(4)-O(2) bond length is 1.96 Å. The Cr(4)-O(6) bond length is 2.06 Å. The Cr(4)-O(7) bond length is 1.97 Å. The Cr(4)-O(9) bond length is 2.06 Å. In the fifth Cr site, Cr(5) is bonded to one O(10), one O(11), one O(3), one O(4), one O(5), and one O(7) atom to form CrO6 octahedra that share corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with two equivalent Cr(2)O5 trigonal bipyramids, edges with two equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(6)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. The Cr(5)-O(10) bond length is 1.92 Å. The Cr(5)-O(11) bond length is 1.93 Å. The Cr(5)-O(3) bond length is 1.93 Å. The Cr(5)-O(4) bond length is 2.03 Å. The Cr(5)-O(5) bond length is 2.03 Å. The Cr(5)-O(7) bond length is 1.93 Å. In the sixth Cr site, Cr(6) is bonded to one O(10), one O(11), one O(2), one O(4), one O(5), and one O(8) atom to form CrO6 octahedra that share corners with two equivalent Cr(3)O6 octahedra, corners with two equivalent Cr(4)O6 octahedra, corners with two equivalent Cr(2)O5 trigonal bipyramids, edges with two equivalent Na(1)O12 cuboctahedra, edges with two equivalent Cr(1)O6 octahedra, and edges with two equivalent Cr(5)O6 octahedra. The corner-sharing octahedral tilt angles are 54°. The Cr(6)-O(10) bond length is 1.93 Å. The Cr(6)-O(11) bond length is 1.94 Å. The Cr(6)-O(2) bond length is 1.94 Å. The Cr(6)-O(4) bond length is 2.03 Å. The Cr(6)-O(5) bond length is 2.03 Å. The Cr(6)-O(8) bond length is 1.93 Å. There are eleven inequivalent O sites. In the first O site, O(5) is bonded in a rectangular see-saw-like geometry to one Cr(1), one Cr(2), one Cr(5), and one Cr(6) atom. In the second O site, O(6) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Cr(2), one Cr(3), and one Cr(4) atom. In the third O site, O(7) is bonded in a 4-coordinate geometry to one Na(1), one Cr(1), one Cr(4), and one Cr(5) atom. In the fourth O site, O(8) is bonded in a 3-coordinate geometry to one Na(1), one Cr(1), one Cr(3), and one Cr(6) atom. In the fifth O site, O(9) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Cr(2), one Cr(3), and one Cr(4) atom. In the sixth O site, O(10) is bonded in a 3-coordinate geometry to one Na(1), one Cr(3), one Cr(5), and one Cr(6) atom. In the seventh O site, O(11) is bonded in a 4-coordinate geometry to one Na(1), one Cr(4), one Cr(5), and one Cr(6) atom. In the eighth O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1), one Cr(2), one Cr(3), and one Cr(4) atom. In the ninth O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Cr(1), one Cr(4), and one Cr(6) atom. In the tenth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Cr(1), one Cr(3), and one Cr(5) atom. In the eleventh O site, O(4) is bonded in a rectangular see-saw-like geometry to one Cr(1), one Cr(2), one Cr(5), and one Cr(6) atom.