K4MgV4O10 crystallizes in the triclinic P1 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(5), one O(7), and one O(9) atom. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. In the third K site, K(3) is bonded in a 7-coordinate geometry to one O(10), one O(2), one O(3), one O(4), one O(5), and two equivalent O(7) atoms. In the fourth K site, K(4) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(6), and one O(8) atom. Mg(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(6), one O(8), and one O(9) atom. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form distorted corner-sharing VO5 square pyramids. In the second V site, V(2) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form VO4 tetrahedra that share corners with two equivalent V(1)O5 square pyramids and  a cornercorner with one V(4)O4 tetrahedra. In the third V site, V(3) is bonded to one O(10), one O(5), one O(8), and one O(9) atom to form distorted VO4 tetrahedra that share  a cornercorner with one V(1)O5 square pyramid and corners with two equivalent V(4)O4 tetrahedra. In the fourth V site, V(4) is bonded to one O(10), one O(6), one O(7), and one O(9) atom to form VO4 tetrahedra that share  a cornercorner with one V(1)O5 square pyramid,  a cornercorner with one V(2)O4 tetrahedra, and corners with two equivalent V(3)O4 tetrahedra. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(1), one Mg(1), one V(1), and one V(2) atom. In the second O site, O(2) is bonded in a distorted trigonal bipyramidal geometry to one K(1), one K(2), one K(3), one K(4), and one V(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one K(1), one K(2), one K(3), one K(4), and one V(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one K(2), one K(3), one K(4), one V(1), and one V(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(3), one V(1), and one V(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one K(2), one K(4), one Mg(1), one V(1), and one V(4) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), two equivalent K(3), one V(2), and one V(4) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one K(2), one K(4), one Mg(1), and one V(3) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one K(1), one Mg(1), one V(3), and one V(4) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one K(1), one K(2), one K(3), one V(3), and one V(4) atom.
K4MgV4O10 crystallizes in the triclinic P1 space group. There are four inequivalent K sites. In the first K site, K(1) is bonded in a 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(5), one O(7), and one O(9) atom. The K(1)-O(1) bond length is 2.72 Å. The K(1)-O(10) bond length is 3.14 Å. The K(1)-O(2) bond length is 2.73 Å. The K(1)-O(3) bond length is 2.78 Å. The K(1)-O(5) bond length is 2.86 Å. The K(1)-O(7) bond length is 2.82 Å. The K(1)-O(9) bond length is 2.88 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(10), one O(2), one O(3), one O(4), one O(6), and one O(8) atom. The K(2)-O(10) bond length is 2.80 Å. The K(2)-O(2) bond length is 2.63 Å. The K(2)-O(3) bond length is 2.77 Å. The K(2)-O(4) bond length is 2.82 Å. The K(2)-O(6) bond length is 3.01 Å. The K(2)-O(8) bond length is 2.82 Å. In the third K site, K(3) is bonded in a 7-coordinate geometry to one O(10), one O(2), one O(3), one O(4), one O(5), and two equivalent O(7) atoms. The K(3)-O(10) bond length is 2.71 Å. The K(3)-O(2) bond length is 2.67 Å. The K(3)-O(3) bond length is 2.71 Å. The K(3)-O(4) bond length is 2.82 Å. The K(3)-O(5) bond length is 2.92 Å. There is one shorter (3.13 Å) and one longer (3.28 Å) K(3)-O(7) bond length. In the fourth K site, K(4) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(4), one O(6), and one O(8) atom. The K(4)-O(2) bond length is 2.76 Å. The K(4)-O(3) bond length is 2.72 Å. The K(4)-O(4) bond length is 2.61 Å. The K(4)-O(6) bond length is 2.72 Å. The K(4)-O(8) bond length is 2.56 Å. Mg(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(6), one O(8), and one O(9) atom. The Mg(1)-O(1) bond length is 1.92 Å. The Mg(1)-O(6) bond length is 2.03 Å. The Mg(1)-O(8) bond length is 2.03 Å. The Mg(1)-O(9) bond length is 2.05 Å. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(4), one O(5), and one O(6) atom to form distorted corner-sharing VO5 square pyramids. The V(1)-O(1) bond length is 2.08 Å. The V(1)-O(3) bond length is 1.70 Å. The V(1)-O(4) bond length is 1.95 Å. The V(1)-O(5) bond length is 2.00 Å. The V(1)-O(6) bond length is 2.12 Å. In the second V site, V(2) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form VO4 tetrahedra that share corners with two equivalent V(1)O5 square pyramids and  a cornercorner with one V(4)O4 tetrahedra. The V(2)-O(1) bond length is 2.04 Å. The V(2)-O(2) bond length is 1.79 Å. The V(2)-O(4) bond length is 2.00 Å. The V(2)-O(7) bond length is 2.02 Å. In the third V site, V(3) is bonded to one O(10), one O(5), one O(8), and one O(9) atom to form distorted VO4 tetrahedra that share  a cornercorner with one V(1)O5 square pyramid and corners with two equivalent V(4)O4 tetrahedra. The V(3)-O(10) bond length is 1.87 Å. The V(3)-O(5) bond length is 1.76 Å. The V(3)-O(8) bond length is 1.81 Å. The V(3)-O(9) bond length is 1.90 Å. In the fourth V site, V(4) is bonded to one O(10), one O(6), one O(7), and one O(9) atom to form VO4 tetrahedra that share  a cornercorner with one V(1)O5 square pyramid,  a cornercorner with one V(2)O4 tetrahedra, and corners with two equivalent V(3)O4 tetrahedra. The V(4)-O(10) bond length is 2.00 Å. The V(4)-O(6) bond length is 2.01 Å. The V(4)-O(7) bond length is 1.85 Å. The V(4)-O(9) bond length is 1.94 Å. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one K(1), one Mg(1), one V(1), and one V(2) atom. In the second O site, O(2) is bonded in a distorted trigonal bipyramidal geometry to one K(1), one K(2), one K(3), one K(4), and one V(2) atom. In the third O site, O(3) is bonded in a distorted single-bond geometry to one K(1), one K(2), one K(3), one K(4), and one V(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one K(2), one K(3), one K(4), one V(1), and one V(2) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one K(1), one K(3), one V(1), and one V(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one K(2), one K(4), one Mg(1), one V(1), and one V(4) atom. In the seventh O site, O(7) is bonded in a 2-coordinate geometry to one K(1), two equivalent K(3), one V(2), and one V(4) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to one K(2), one K(4), one Mg(1), and one V(3) atom. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one K(1), one Mg(1), one V(3), and one V(4) atom. In the tenth O site, O(10) is bonded in a 5-coordinate geometry to one K(1), one K(2), one K(3), one V(3), and one V(4) atom.