Na3Fe2Mo5O16 crystallizes in the trigonal P-3m1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(5) and three equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(8) and three equivalent O(3) atoms. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. There are three inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(5) and three equivalent O(1) atoms to form MoO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 21°. In the second Mo site, Mo(2) is bonded to one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms to form MoO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with four equivalent Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-53°. In the third Mo site, Mo(3) is bonded in a 5-coordinate geometry to one O(6), one O(8), and three equivalent O(2) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Mo(2)O6 octahedra and corners with three equivalent Mo(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. In the second Fe site, Fe(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. There are eight inequivalent O sites. In the first O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Mo(3) and three equivalent Mo(2) atoms. In the second O site, O(7) is bonded in a 3-coordinate geometry to three equivalent Mo(2) atoms. In the third O site, O(8) is bonded in a linear geometry to one Na(3) and one Mo(3) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Na(4), one Mo(1), and one Fe(1) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Mo(3), and one Fe(2) atom. In the sixth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Na(3), two equivalent Mo(2), and one Fe(2) atom. In the seventh O site, O(4) is bonded to one Na(1), two equivalent Mo(2), and one Fe(1) atom to form a mixture of edge and corner-sharing ONaFeMo2 trigonal pyramids. In the eighth O site, O(5) is bonded in a linear geometry to one Na(1) and one Mo(1) atom.
Na3Fe2Mo5O16 crystallizes in the trigonal P-3m1 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(5) and three equivalent O(4) atoms. The Na(1)-O(5) bond length is 2.20 Å. All Na(1)-O(4) bond lengths are 2.49 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. All Na(2)-O(2) bond lengths are 2.60 Å. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(8) and three equivalent O(3) atoms. The Na(3)-O(8) bond length is 2.27 Å. All Na(3)-O(3) bond lengths are 2.49 Å. In the fourth Na site, Na(4) is bonded in a 6-coordinate geometry to six equivalent O(1) atoms. All Na(4)-O(1) bond lengths are 2.62 Å. There are three inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(5) and three equivalent O(1) atoms to form MoO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 21°. The Mo(1)-O(5) bond length is 1.76 Å. All Mo(1)-O(1) bond lengths are 1.82 Å. In the second Mo site, Mo(2) is bonded to one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms to form MoO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with four equivalent Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 52-53°. The Mo(2)-O(6) bond length is 2.13 Å. The Mo(2)-O(7) bond length is 2.09 Å. Both Mo(2)-O(3) bond lengths are 2.09 Å. Both Mo(2)-O(4) bond lengths are 2.02 Å. In the third Mo site, Mo(3) is bonded in a 5-coordinate geometry to one O(6), one O(8), and three equivalent O(2) atoms. The Mo(3)-O(6) bond length is 2.49 Å. The Mo(3)-O(8) bond length is 1.76 Å. All Mo(3)-O(2) bond lengths are 1.85 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Mo(2)O6 octahedra and corners with three equivalent Mo(1)O4 tetrahedra. The corner-sharing octahedral tilt angles are 52°. All Fe(1)-O(1) bond lengths are 2.16 Å. All Fe(1)-O(4) bond lengths are 2.21 Å. In the second Fe site, Fe(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form FeO6 octahedra that share corners with six equivalent Mo(2)O6 octahedra. The corner-sharing octahedral tilt angles are 53°. All Fe(2)-O(2) bond lengths are 2.15 Å. All Fe(2)-O(3) bond lengths are 2.04 Å. There are eight inequivalent O sites. In the first O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Mo(3) and three equivalent Mo(2) atoms. In the second O site, O(7) is bonded in a 3-coordinate geometry to three equivalent Mo(2) atoms. In the third O site, O(8) is bonded in a linear geometry to one Na(3) and one Mo(3) atom. In the fourth O site, O(1) is bonded in a 3-coordinate geometry to one Na(4), one Mo(1), and one Fe(1) atom. In the fifth O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Mo(3), and one Fe(2) atom. In the sixth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Na(3), two equivalent Mo(2), and one Fe(2) atom. In the seventh O site, O(4) is bonded to one Na(1), two equivalent Mo(2), and one Fe(1) atom to form a mixture of edge and corner-sharing ONaFeMo2 trigonal pyramids. In the eighth O site, O(5) is bonded in a linear geometry to one Na(1) and one Mo(1) atom.