K3Na(FeO4)2 crystallizes in the trigonal P-3m1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. In the second K site, K(2) is bonded in a 10-coordinate geometry to one O(1) and nine equivalent O(2) atoms. Na(1) is bonded to six equivalent O(2) atoms to form NaO6 octahedra that share corners with six equivalent Fe(1)O4 tetrahedra. Fe(1) is bonded to one O(1) and three equivalent O(2) atoms to form FeO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles are 18°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one K(2) and one Fe(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one K(1), three equivalent K(2), one Na(1), and one Fe(1) atom.
K3Na(FeO4)2 crystallizes in the trigonal P-3m1 space group. There are two inequivalent K sites. In the first K site, K(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. All K(1)-O(2) bond lengths are 2.98 Å. In the second K site, K(2) is bonded in a 10-coordinate geometry to one O(1) and nine equivalent O(2) atoms. The K(2)-O(1) bond length is 2.66 Å. There are six shorter (2.97 Å) and three longer (3.17 Å) K(2)-O(2) bond lengths. Na(1) is bonded to six equivalent O(2) atoms to form NaO6 octahedra that share corners with six equivalent Fe(1)O4 tetrahedra. All Na(1)-O(2) bond lengths are 2.38 Å. Fe(1) is bonded to one O(1) and three equivalent O(2) atoms to form FeO4 tetrahedra that share corners with three equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles are 18°. The Fe(1)-O(1) bond length is 1.64 Å. All Fe(1)-O(2) bond lengths are 1.67 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to one K(2) and one Fe(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one K(1), three equivalent K(2), one Na(1), and one Fe(1) atom.