Na2Cr4O13 crystallizes in the monoclinic Pc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(2), and one O(4) atom. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one O(10), one O(11), and two equivalent O(13) atoms. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(13), one O(2), and one O(3) atom to form corner-sharing CrO4 tetrahedra. In the second Cr site, Cr(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form corner-sharing CrO4 tetrahedra. In the third Cr site, Cr(3) is bonded to one O(4), one O(5), one O(7), and one O(9) atom to form corner-sharing CrO4 tetrahedra. In the fourth Cr site, Cr(4) is bonded to one O(10), one O(11), one O(12), and one O(9) atom to form corner-sharing CrO4 tetrahedra. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Na(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Cr(1) and one Cr(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Na(1) and one Cr(3) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Cr(3) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one Cr(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one Cr(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Cr(3) and one Cr(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Na(2) and one Cr(4) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Na(1), one Na(2), and one Cr(4) atom. In the twelfth O site, O(12) is bonded in a 1-coordinate geometry to one Na(1) and one Cr(4) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one Na(1), two equivalent Na(2), and one Cr(1) atom.
Na2Cr4O13 crystallizes in the monoclinic Pc space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(11), one O(12), one O(13), one O(2), and one O(4) atom. The Na(1)-O(1) bond length is 2.57 Å. The Na(1)-O(11) bond length is 2.97 Å. The Na(1)-O(12) bond length is 2.48 Å. The Na(1)-O(13) bond length is 2.82 Å. The Na(1)-O(2) bond length is 2.57 Å. The Na(1)-O(4) bond length is 2.80 Å. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one O(10), one O(11), and two equivalent O(13) atoms. The Na(2)-O(10) bond length is 2.53 Å. The Na(2)-O(11) bond length is 2.58 Å. There is one shorter (2.60 Å) and one longer (2.70 Å) Na(2)-O(13) bond length. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(1), one O(13), one O(2), and one O(3) atom to form corner-sharing CrO4 tetrahedra. The Cr(1)-O(1) bond length is 1.63 Å. The Cr(1)-O(13) bond length is 1.64 Å. The Cr(1)-O(2) bond length is 1.62 Å. The Cr(1)-O(3) bond length is 1.84 Å. In the second Cr site, Cr(2) is bonded to one O(3), one O(6), one O(7), and one O(8) atom to form corner-sharing CrO4 tetrahedra. The Cr(2)-O(3) bond length is 1.75 Å. The Cr(2)-O(6) bond length is 1.59 Å. The Cr(2)-O(7) bond length is 1.77 Å. The Cr(2)-O(8) bond length is 1.61 Å. In the third Cr site, Cr(3) is bonded to one O(4), one O(5), one O(7), and one O(9) atom to form corner-sharing CrO4 tetrahedra. The Cr(3)-O(4) bond length is 1.61 Å. The Cr(3)-O(5) bond length is 1.59 Å. The Cr(3)-O(7) bond length is 1.78 Å. The Cr(3)-O(9) bond length is 1.73 Å. In the fourth Cr site, Cr(4) is bonded to one O(10), one O(11), one O(12), and one O(9) atom to form corner-sharing CrO4 tetrahedra. The Cr(4)-O(10) bond length is 1.63 Å. The Cr(4)-O(11) bond length is 1.63 Å. The Cr(4)-O(12) bond length is 1.64 Å. The Cr(4)-O(9) bond length is 1.82 Å. There are thirteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Na(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Cr(1) and one Cr(2) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Na(1) and one Cr(3) atom. In the fifth O site, O(5) is bonded in a single-bond geometry to one Cr(3) atom. In the sixth O site, O(6) is bonded in a single-bond geometry to one Cr(2) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one Cr(2) and one Cr(3) atom. In the eighth O site, O(8) is bonded in a single-bond geometry to one Cr(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Cr(3) and one Cr(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Na(2) and one Cr(4) atom. In the eleventh O site, O(11) is bonded in a distorted single-bond geometry to one Na(1), one Na(2), and one Cr(4) atom. In the twelfth O site, O(12) is bonded in a 1-coordinate geometry to one Na(1) and one Cr(4) atom. In the thirteenth O site, O(13) is bonded in a distorted single-bond geometry to one Na(1), two equivalent Na(2), and one Cr(1) atom.