K3Na(SeO4)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and four equivalent O(4) atoms. In the second K site, K(2) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(2), three equivalent O(1), and three equivalent O(3) atoms. Na(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NaO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SeO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-38°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 6-coordinate geometry to one K(1), three equivalent K(2), one Na(1), and one Se(1) atom. In the second O site, O(4) is bonded in a 3-coordinate geometry to one K(2), two equivalent K(1), and one Se(1) atom. In the third O site, O(1) is bonded in a 6-coordinate geometry to one K(1), three equivalent K(2), one Na(1), and one Se(1) atom. In the fourth O site, O(2) is bonded in a 5-coordinate geometry to one K(1), two equivalent K(2), one Na(1), and one Se(1) atom.
K3Na(SeO4)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 10-coordinate geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and four equivalent O(4) atoms. Both K(1)-O(1) bond lengths are 3.00 Å. Both K(1)-O(2) bond lengths are 2.77 Å. Both K(1)-O(3) bond lengths are 3.08 Å. There are two shorter (2.91 Å) and two longer (3.35 Å) K(1)-O(4) bond lengths. In the second K site, K(2) is bonded in a 9-coordinate geometry to one O(4), two equivalent O(2), three equivalent O(1), and three equivalent O(3) atoms. The K(2)-O(4) bond length is 2.59 Å. There is one shorter (2.94 Å) and one longer (2.95 Å) K(2)-O(2) bond length. There are a spread of K(2)-O(1) bond distances ranging from 2.84-3.08 Å. There are a spread of K(2)-O(3) bond distances ranging from 2.86-2.96 Å. Na(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NaO6 octahedra that share corners with six equivalent Se(1)O4 tetrahedra. Both Na(1)-O(1) bond lengths are 2.34 Å. Both Na(1)-O(2) bond lengths are 2.40 Å. Both Na(1)-O(3) bond lengths are 2.34 Å. Se(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SeO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-38°. The Se(1)-O(1) bond length is 1.66 Å. The Se(1)-O(2) bond length is 1.66 Å. The Se(1)-O(3) bond length is 1.66 Å. The Se(1)-O(4) bond length is 1.64 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 6-coordinate geometry to one K(1), three equivalent K(2), one Na(1), and one Se(1) atom. In the second O site, O(4) is bonded in a 3-coordinate geometry to one K(2), two equivalent K(1), and one Se(1) atom. In the third O site, O(1) is bonded in a 6-coordinate geometry to one K(1), three equivalent K(2), one Na(1), and one Se(1) atom. In the fourth O site, O(2) is bonded in a 5-coordinate geometry to one K(1), two equivalent K(2), one Na(1), and one Se(1) atom.