Na3CaFe(SiO3)8 crystallizes in the monoclinic C2 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to two equivalent O(12) and two equivalent O(5) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(11), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. Fe(1) is bonded to two equivalent O(5), two equivalent O(7), and two equivalent O(9) atoms to form FeO6 octahedra that share corners with two equivalent Si(3)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 27-46°. In the second Si site, Si(2) is bonded to one O(10), one O(2), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(11), one O(2), one O(3), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the fourth Si site, Si(4) is bonded to one O(1), one O(12), one O(4), and one O(8) atom to form corner-sharing SiO4 tetrahedra. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1), one Si(2), and one Si(3) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(2), one Si(1), and one Si(3) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Na(2), one Ca(1), one Si(2), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Fe(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(2), one Fe(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Na(2) and one Si(4) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Na(2), one Fe(1), and one Si(1) atom. In the tenth O site, O(10) is bonded in a distorted water-like geometry to one Na(2) and one Si(2) atom. In the eleventh O site, O(11) is bonded in a water-like geometry to one Ca(1) and one Si(3) atom. In the twelfth O site, O(12) is bonded in a water-like geometry to one Na(1) and one Si(4) atom.
Na3CaFe(SiO3)8 crystallizes in the monoclinic C2 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to two equivalent O(12) and two equivalent O(5) atoms. Both Na(1)-O(12) bond lengths are 2.47 Å. Both Na(1)-O(5) bond lengths are 2.32 Å. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(10), one O(3), one O(4), one O(7), one O(8), and one O(9) atom. The Na(2)-O(10) bond length is 2.47 Å. The Na(2)-O(3) bond length is 2.64 Å. The Na(2)-O(4) bond length is 2.59 Å. The Na(2)-O(7) bond length is 2.36 Å. The Na(2)-O(8) bond length is 2.25 Å. The Na(2)-O(9) bond length is 2.48 Å. Ca(1) is bonded in a 8-coordinate geometry to two equivalent O(11), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. Both Ca(1)-O(11) bond lengths are 2.42 Å. Both Ca(1)-O(2) bond lengths are 2.64 Å. Both Ca(1)-O(4) bond lengths are 3.00 Å. Both Ca(1)-O(6) bond lengths are 2.23 Å. Fe(1) is bonded to two equivalent O(5), two equivalent O(7), and two equivalent O(9) atoms to form FeO6 octahedra that share corners with two equivalent Si(3)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. Both Fe(1)-O(5) bond lengths are 2.05 Å. Both Fe(1)-O(7) bond lengths are 2.00 Å. Both Fe(1)-O(9) bond lengths are 2.15 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(5), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Fe(1)O6 octahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 27-46°. The Si(1)-O(1) bond length is 1.67 Å. The Si(1)-O(3) bond length is 1.69 Å. The Si(1)-O(5) bond length is 1.63 Å. The Si(1)-O(9) bond length is 1.63 Å. In the second Si site, Si(2) is bonded to one O(10), one O(2), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(10) bond length is 1.64 Å. The Si(2)-O(2) bond length is 1.64 Å. The Si(2)-O(4) bond length is 1.67 Å. The Si(2)-O(6) bond length is 1.60 Å. In the third Si site, Si(3) is bonded to one O(11), one O(2), one O(3), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 53°. The Si(3)-O(11) bond length is 1.62 Å. The Si(3)-O(2) bond length is 1.69 Å. The Si(3)-O(3) bond length is 1.66 Å. The Si(3)-O(7) bond length is 1.63 Å. In the fourth Si site, Si(4) is bonded to one O(1), one O(12), one O(4), and one O(8) atom to form corner-sharing SiO4 tetrahedra. The Si(4)-O(1) bond length is 1.64 Å. The Si(4)-O(12) bond length is 1.63 Å. The Si(4)-O(4) bond length is 1.65 Å. The Si(4)-O(8) bond length is 1.63 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Si(1) and one Si(4) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1), one Si(2), and one Si(3) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(2), one Si(1), and one Si(3) atom. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Na(2), one Ca(1), one Si(2), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Fe(1), and one Si(1) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(2), one Fe(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 150 degrees geometry to one Na(2) and one Si(4) atom. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Na(2), one Fe(1), and one Si(1) atom. In the tenth O site, O(10) is bonded in a distorted water-like geometry to one Na(2) and one Si(2) atom. In the eleventh O site, O(11) is bonded in a water-like geometry to one Ca(1) and one Si(3) atom. In the twelfth O site, O(12) is bonded in a water-like geometry to one Na(1) and one Si(4) atom.