NaCa3Fe4(SiO3)8 crystallizes in the monoclinic C2 space group. Na(1) is bonded in a 6-coordinate geometry to two equivalent O(11), two equivalent O(5), and two equivalent O(9) atoms. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(6), and two equivalent O(7) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(10), one O(12), one O(2), one O(3), one O(4), and one O(8) atom. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(4) and two equivalent O(8) atoms. In the second Fe site, Fe(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(5), one O(7), and one O(9) atom. In the third Fe site, Fe(3) is bonded to two equivalent O(12), two equivalent O(2), and two equivalent O(5) atoms to form distorted FeO6 pentagonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra and edges with two equivalent Si(2)O4 tetrahedra. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(11), one O(2), one O(3), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(3)O6 pentagonal pyramid,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(12), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  an edgeedge with one Fe(3)O6 pentagonal pyramid. In the third Si site, Si(3) is bonded to one O(10), one O(6), one O(7), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(1), one O(10), one O(11), and one O(4) atom to form corner-sharing SiO4 tetrahedra. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(2), and one Si(4) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(2), one Fe(3), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Ca(2), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(2), one Fe(1), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted see-saw-like geometry to one Na(1), one Fe(2), one Fe(3), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(2), and one Si(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(2), one Fe(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(1), one Fe(2), and one Si(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Ca(2), one Si(3), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Na(1), one Si(1), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Ca(2), one Fe(3), and one Si(2) atom.
NaCa3Fe4(SiO3)8 crystallizes in the monoclinic C2 space group. Na(1) is bonded in a 6-coordinate geometry to two equivalent O(11), two equivalent O(5), and two equivalent O(9) atoms. Both Na(1)-O(11) bond lengths are 2.59 Å. Both Na(1)-O(5) bond lengths are 2.39 Å. Both Na(1)-O(9) bond lengths are 2.58 Å. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(6), and two equivalent O(7) atoms. Both Ca(1)-O(1) bond lengths are 2.25 Å. Both Ca(1)-O(6) bond lengths are 2.88 Å. Both Ca(1)-O(7) bond lengths are 2.38 Å. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(10), one O(12), one O(2), one O(3), one O(4), and one O(8) atom. The Ca(2)-O(10) bond length is 2.89 Å. The Ca(2)-O(12) bond length is 2.37 Å. The Ca(2)-O(2) bond length is 2.25 Å. The Ca(2)-O(3) bond length is 2.80 Å. The Ca(2)-O(4) bond length is 2.37 Å. The Ca(2)-O(8) bond length is 2.29 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a rectangular see-saw-like geometry to two equivalent O(4) and two equivalent O(8) atoms. Both Fe(1)-O(4) bond lengths are 2.04 Å. Both Fe(1)-O(8) bond lengths are 1.98 Å. In the second Fe site, Fe(2) is bonded in a rectangular see-saw-like geometry to one O(1), one O(5), one O(7), and one O(9) atom. The Fe(2)-O(1) bond length is 2.02 Å. The Fe(2)-O(5) bond length is 2.03 Å. The Fe(2)-O(7) bond length is 2.04 Å. The Fe(2)-O(9) bond length is 2.00 Å. In the third Fe site, Fe(3) is bonded to two equivalent O(12), two equivalent O(2), and two equivalent O(5) atoms to form distorted FeO6 pentagonal pyramids that share corners with two equivalent Si(1)O4 tetrahedra and edges with two equivalent Si(2)O4 tetrahedra. Both Fe(3)-O(12) bond lengths are 2.07 Å. Both Fe(3)-O(2) bond lengths are 1.95 Å. Both Fe(3)-O(5) bond lengths are 2.22 Å. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(11), one O(2), one O(3), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Fe(3)O6 pentagonal pyramid,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(4)O4 tetrahedra. The Si(1)-O(11) bond length is 1.69 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.71 Å. The Si(1)-O(9) bond length is 1.61 Å. In the second Si site, Si(2) is bonded to one O(12), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)O4 tetrahedra, and  an edgeedge with one Fe(3)O6 pentagonal pyramid. The Si(2)-O(12) bond length is 1.65 Å. The Si(2)-O(3) bond length is 1.71 Å. The Si(2)-O(5) bond length is 1.64 Å. The Si(2)-O(6) bond length is 1.68 Å. In the third Si site, Si(3) is bonded to one O(10), one O(6), one O(7), and one O(8) atom to form corner-sharing SiO4 tetrahedra. The Si(3)-O(10) bond length is 1.70 Å. The Si(3)-O(6) bond length is 1.72 Å. The Si(3)-O(7) bond length is 1.63 Å. The Si(3)-O(8) bond length is 1.62 Å. In the fourth Si site, Si(4) is bonded to one O(1), one O(10), one O(11), and one O(4) atom to form corner-sharing SiO4 tetrahedra. The Si(4)-O(1) bond length is 1.63 Å. The Si(4)-O(10) bond length is 1.72 Å. The Si(4)-O(11) bond length is 1.70 Å. The Si(4)-O(4) bond length is 1.63 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(2), and one Si(4) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ca(2), one Fe(3), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted water-like geometry to one Ca(2), one Si(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ca(2), one Fe(1), and one Si(4) atom. In the fifth O site, O(5) is bonded in a distorted see-saw-like geometry to one Na(1), one Fe(2), one Fe(3), and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Ca(1), one Si(2), and one Si(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Ca(2), one Fe(1), and one Si(3) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(1), one Fe(2), and one Si(1) atom. In the tenth O site, O(10) is bonded in a distorted bent 120 degrees geometry to one Ca(2), one Si(3), and one Si(4) atom. In the eleventh O site, O(11) is bonded in a distorted trigonal non-coplanar geometry to one Na(1), one Si(1), and one Si(4) atom. In the twelfth O site, O(12) is bonded in a distorted T-shaped geometry to one Ca(2), one Fe(3), and one Si(2) atom.