Na4MgCr2O8 crystallizes in the triclinic P-1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form distorted edge-sharing NaO5 trigonal bipyramids. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), and two equivalent O(4) atoms. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Cr(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Mg(1), and one Cr(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Mg(1), and one Cr(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Mg(1), and one Cr(1) atom.
Na4MgCr2O8 crystallizes in the triclinic P-1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to one O(2), one O(3), one O(4), and two equivalent O(1) atoms to form distorted edge-sharing NaO5 trigonal bipyramids. The Na(1)-O(2) bond length is 2.28 Å. The Na(1)-O(3) bond length is 2.72 Å. The Na(1)-O(4) bond length is 2.37 Å. There is one shorter (2.34 Å) and one longer (2.43 Å) Na(1)-O(1) bond length. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(2), two equivalent O(3), and two equivalent O(4) atoms. The Na(2)-O(2) bond length is 2.89 Å. There is one shorter (2.31 Å) and one longer (2.42 Å) Na(2)-O(3) bond length. There is one shorter (2.33 Å) and one longer (2.75 Å) Na(2)-O(4) bond length. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms. Both Mg(1)-O(2) bond lengths are 2.34 Å. Both Mg(1)-O(3) bond lengths are 2.16 Å. Both Mg(1)-O(4) bond lengths are 2.08 Å. Cr(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. The Cr(1)-O(1) bond length is 1.66 Å. The Cr(1)-O(2) bond length is 1.70 Å. The Cr(1)-O(3) bond length is 1.79 Å. The Cr(1)-O(4) bond length is 1.80 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to two equivalent Na(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Mg(1), and one Cr(1) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Mg(1), and one Cr(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), two equivalent Na(2), one Mg(1), and one Cr(1) atom.