K4MgV6O16 crystallizes in the orthorhombic Cmm2 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 3-coordinate geometry to one O(5) and two equivalent O(7) atoms. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms. Mg(1) is bonded in a trigonal planar geometry to one O(2) and two equivalent O(4) atoms. There are three inequivalent V sites. In the first V site, V(1) is bonded to one O(3), one O(5), and two equivalent O(7) atoms to form VO4 tetrahedra that share  a cornercorner with one V(1)O4 tetrahedra and corners with two equivalent V(3)O5 trigonal bipyramids. In the second V site, V(2) is bonded to one O(2), one O(4), and two equivalent O(6) atoms to form VO4 tetrahedra that share  a cornercorner with one V(2)O4 tetrahedra and corners with two equivalent V(3)O5 trigonal bipyramids. In the third V site, V(3) is bonded to one O(1), two equivalent O(6), and two equivalent O(7) atoms to form distorted corner-sharing VO5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 3-coordinate geometry to one K(1), one V(1), and one V(3) atom. In the second O site, O(1) is bonded in a single-bond geometry to one V(3) atom. In the third O site, O(2) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent V(2) atoms. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent K(2) and two equivalent V(1) atoms. In the fifth O site, O(4) is bonded in a distorted trigonal planar geometry to one K(2), one Mg(1), and one V(2) atom. In the sixth O site, O(5) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one V(1) atom. In the seventh O site, O(6) is bonded in a distorted bent 150 degrees geometry to one K(2), one V(2), and one V(3) atom.
K4MgV6O16 crystallizes in the orthorhombic Cmm2 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 3-coordinate geometry to one O(5) and two equivalent O(7) atoms. The K(1)-O(5) bond length is 2.55 Å. Both K(1)-O(7) bond lengths are 2.69 Å. In the second K site, K(2) is bonded in a 6-coordinate geometry to one O(3), one O(4), two equivalent O(5), and two equivalent O(6) atoms. The K(2)-O(3) bond length is 2.94 Å. The K(2)-O(4) bond length is 2.77 Å. Both K(2)-O(5) bond lengths are 2.99 Å. Both K(2)-O(6) bond lengths are 3.02 Å. Mg(1) is bonded in a trigonal planar geometry to one O(2) and two equivalent O(4) atoms. The Mg(1)-O(2) bond length is 1.94 Å. Both Mg(1)-O(4) bond lengths are 1.88 Å. There are three inequivalent V sites. In the first V site, V(1) is bonded to one O(3), one O(5), and two equivalent O(7) atoms to form VO4 tetrahedra that share  a cornercorner with one V(1)O4 tetrahedra and corners with two equivalent V(3)O5 trigonal bipyramids. The V(1)-O(3) bond length is 1.83 Å. The V(1)-O(5) bond length is 1.67 Å. Both V(1)-O(7) bond lengths are 1.74 Å. In the second V site, V(2) is bonded to one O(2), one O(4), and two equivalent O(6) atoms to form VO4 tetrahedra that share  a cornercorner with one V(2)O4 tetrahedra and corners with two equivalent V(3)O5 trigonal bipyramids. The V(2)-O(2) bond length is 1.93 Å. The V(2)-O(4) bond length is 1.83 Å. Both V(2)-O(6) bond lengths are 1.79 Å. In the third V site, V(3) is bonded to one O(1), two equivalent O(6), and two equivalent O(7) atoms to form distorted corner-sharing VO5 trigonal bipyramids. The V(3)-O(1) bond length is 1.65 Å. Both V(3)-O(6) bond lengths are 2.00 Å. Both V(3)-O(7) bond lengths are 2.01 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded in a 3-coordinate geometry to one K(1), one V(1), and one V(3) atom. In the second O site, O(1) is bonded in a single-bond geometry to one V(3) atom. In the third O site, O(2) is bonded in a trigonal planar geometry to one Mg(1) and two equivalent V(2) atoms. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to two equivalent K(2) and two equivalent V(1) atoms. In the fifth O site, O(4) is bonded in a distorted trigonal planar geometry to one K(2), one Mg(1), and one V(2) atom. In the sixth O site, O(5) is bonded in a 4-coordinate geometry to one K(1), two equivalent K(2), and one V(1) atom. In the seventh O site, O(6) is bonded in a distorted bent 150 degrees geometry to one K(2), one V(2), and one V(3) atom.