NaFe2(SiO3)4 crystallizes in the monoclinic C2 space group. Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Fe(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-59°. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-59°. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Fe(1), one Fe(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one Si(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1), one Fe(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(1), and one Si(2) atom.
NaFe2(SiO3)4 crystallizes in the monoclinic C2 space group. Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Both Na(1)-O(1) bond lengths are 2.40 Å. Both Na(1)-O(4) bond lengths are 2.40 Å. Both Na(1)-O(5) bond lengths are 2.43 Å. Both Na(1)-O(6) bond lengths are 2.88 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted FeO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra, corners with four equivalent Si(1)O4 tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. Both Fe(1)-O(1) bond lengths are 2.17 Å. Both Fe(1)-O(2) bond lengths are 2.03 Å. Both Fe(1)-O(3) bond lengths are 1.92 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(5) atoms to form FeO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with four equivalent Si(2)O4 tetrahedra, and edges with two equivalent Fe(1)O6 octahedra. Both Fe(2)-O(1) bond lengths are 2.04 Å. Both Fe(2)-O(2) bond lengths are 2.08 Å. Both Fe(2)-O(5) bond lengths are 1.96 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(2)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-59°. The Si(1)-O(1) bond length is 1.66 Å. The Si(1)-O(3) bond length is 1.61 Å. The Si(1)-O(4) bond length is 1.65 Å. The Si(1)-O(6) bond length is 1.64 Å. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-59°. The Si(2)-O(2) bond length is 1.65 Å. The Si(2)-O(4) bond length is 1.65 Å. The Si(2)-O(5) bond length is 1.63 Å. The Si(2)-O(6) bond length is 1.64 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Fe(1), one Fe(2), and one Si(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(1), one Fe(2), and one Si(2) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Fe(1) and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1), one Fe(2), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(1), and one Si(2) atom.