Na6FeAl4(Si4O13)2 is Chalcostibite-derived structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(6), two equivalent O(1), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(2), and two equivalent O(5) atoms. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(8), two equivalent O(4), and two equivalent O(5) atoms. Fe(1) is bonded in a distorted square co-planar geometry to four equivalent O(1) atoms. Al(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Fe(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(3), one Al(1), and one Si(1) atom. In the fifth O site, O(5) is bonded to one Na(2), one Na(3), one Al(1), and one Si(2) atom to form distorted edge-sharing ONa2AlSi tetrahedra. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(1) and two equivalent Al(1) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2) and two equivalent Si(1) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(3) and two equivalent Si(2) atoms.
Na6FeAl4(Si4O13)2 is Chalcostibite-derived structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(6), two equivalent O(1), and two equivalent O(3) atoms. The Na(1)-O(6) bond length is 2.61 Å. Both Na(1)-O(1) bond lengths are 2.32 Å. Both Na(1)-O(3) bond lengths are 2.53 Å. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(7), two equivalent O(2), and two equivalent O(5) atoms. The Na(2)-O(7) bond length is 2.56 Å. Both Na(2)-O(2) bond lengths are 2.46 Å. Both Na(2)-O(5) bond lengths are 2.50 Å. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(8), two equivalent O(4), and two equivalent O(5) atoms. The Na(3)-O(8) bond length is 2.33 Å. Both Na(3)-O(4) bond lengths are 2.37 Å. Both Na(3)-O(5) bond lengths are 2.51 Å. Fe(1) is bonded in a distorted square co-planar geometry to four equivalent O(1) atoms. All Fe(1)-O(1) bond lengths are 2.06 Å. Al(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form AlO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The Al(1)-O(2) bond length is 1.78 Å. The Al(1)-O(4) bond length is 1.76 Å. The Al(1)-O(5) bond length is 1.77 Å. The Al(1)-O(6) bond length is 1.73 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), one O(4), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. The Si(1)-O(2) bond length is 1.63 Å. The Si(1)-O(3) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.61 Å. The Si(1)-O(7) bond length is 1.66 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The Si(2)-O(1) bond length is 1.60 Å. The Si(2)-O(3) bond length is 1.67 Å. The Si(2)-O(5) bond length is 1.64 Å. The Si(2)-O(8) bond length is 1.70 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Fe(1), and one Si(2) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Al(1), and one Si(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(3), one Al(1), and one Si(1) atom. In the fifth O site, O(5) is bonded to one Na(2), one Na(3), one Al(1), and one Si(2) atom to form distorted edge-sharing ONa2AlSi tetrahedra. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(1) and two equivalent Al(1) atoms. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2) and two equivalent Si(1) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(3) and two equivalent Si(2) atoms.