Na4CaFe4(PO4)6 crystallizes in the monoclinic C2 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(4), one O(9), two equivalent O(12), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(11), two equivalent O(7), and two equivalent O(8) atoms. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(12), and two equivalent O(3) atoms. Ca(1) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(9) atoms to form distorted CaO6 pentagonal pyramids that share corners with two equivalent P(4)O4 tetrahedra and  an edgeedge with one P(2)O4 tetrahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 4-coordinate geometry to one O(2), one O(4), one O(5), and one O(8) atom. In the second Fe site, Fe(2) is bonded in a 5-coordinate geometry to one P(3), one O(10), one O(11), one O(2), and one O(3) atom. There are four inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(1), one O(2), one O(3), and one O(7) atom. In the second P site, P(2) is bonded to two equivalent O(11) and two equivalent O(5) atoms to form PO4 tetrahedra that share  an edgeedge with one Ca(1)O6 pentagonal pyramid. In the third P site, P(3) is bonded in a 3-coordinate geometry to one Fe(2), one O(1), one O(6), and one O(7) atom. In the fourth P site, P(4) is bonded to two equivalent O(8) and two equivalent O(9) atoms to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 pentagonal pyramids. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(3), one P(1), and one P(3) 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 P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(3), one Fe(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Na(1) and one Fe(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Ca(1), and one P(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2), one P(1), and one P(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), and one P(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(1), one Ca(1), and one P(4) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Fe(2) and one O(12) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Na(2), one Fe(2), and one P(2) atom. In the twelfth O site, O(12) is bonded in a distorted see-saw-like geometry to one Na(3), two equivalent Na(1), and one O(10) atom.
Na4CaFe4(PO4)6 crystallizes in the monoclinic C2 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(4), one O(9), two equivalent O(12), and two equivalent O(6) atoms. The Na(1)-O(4) bond length is 2.30 Å. The Na(1)-O(9) bond length is 2.58 Å. There is one shorter (2.44 Å) and one longer (2.49 Å) Na(1)-O(12) bond length. There is one shorter (2.73 Å) and one longer (2.76 Å) Na(1)-O(6) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(11), two equivalent O(7), and two equivalent O(8) atoms. Both Na(2)-O(11) bond lengths are 2.71 Å. Both Na(2)-O(7) bond lengths are 2.51 Å. Both Na(2)-O(8) bond lengths are 2.42 Å. In the third Na site, Na(3) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(12), and two equivalent O(3) atoms. Both Na(3)-O(1) bond lengths are 2.53 Å. Both Na(3)-O(12) bond lengths are 2.30 Å. Both Na(3)-O(3) bond lengths are 2.48 Å. Ca(1) is bonded to two equivalent O(5), two equivalent O(6), and two equivalent O(9) atoms to form distorted CaO6 pentagonal pyramids that share corners with two equivalent P(4)O4 tetrahedra and  an edgeedge with one P(2)O4 tetrahedra. Both Ca(1)-O(5) bond lengths are 2.37 Å. Both Ca(1)-O(6) bond lengths are 2.28 Å. Both Ca(1)-O(9) bond lengths are 2.38 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 4-coordinate geometry to one O(2), one O(4), one O(5), and one O(8) atom. The Fe(1)-O(2) bond length is 2.32 Å. The Fe(1)-O(4) bond length is 1.73 Å. The Fe(1)-O(5) bond length is 2.05 Å. The Fe(1)-O(8) bond length is 1.97 Å. In the second Fe site, Fe(2) is bonded in a 5-coordinate geometry to one P(3), one O(10), one O(11), one O(2), and one O(3) atom. The Fe(2)-P(3) bond length is 2.50 Å. The Fe(2)-O(10) bond length is 2.08 Å. The Fe(2)-O(11) bond length is 2.00 Å. The Fe(2)-O(2) bond length is 2.03 Å. The Fe(2)-O(3) bond length is 2.32 Å. There are four inequivalent P sites. In the first P site, P(1) is bonded in a tetrahedral geometry to one O(1), one O(2), one O(3), and one O(7) atom. The P(1)-O(1) bond length is 1.62 Å. The P(1)-O(2) bond length is 1.54 Å. The P(1)-O(3) bond length is 1.50 Å. The P(1)-O(7) bond length is 1.64 Å. In the second P site, P(2) is bonded to two equivalent O(11) and two equivalent O(5) atoms to form PO4 tetrahedra that share  an edgeedge with one Ca(1)O6 pentagonal pyramid. Both P(2)-O(11) bond lengths are 1.54 Å. Both P(2)-O(5) bond lengths are 1.58 Å. In the third P site, P(3) is bonded in a 3-coordinate geometry to one Fe(2), one O(1), one O(6), and one O(7) atom. The P(3)-O(1) bond length is 1.78 Å. The P(3)-O(6) bond length is 1.51 Å. The P(3)-O(7) bond length is 1.74 Å. In the fourth P site, P(4) is bonded to two equivalent O(8) and two equivalent O(9) atoms to form PO4 tetrahedra that share corners with two equivalent Ca(1)O6 pentagonal pyramids. Both P(4)-O(8) bond lengths are 1.60 Å. Both P(4)-O(9) bond lengths are 1.54 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(3), one P(1), and one P(3) 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 P(1) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(3), one Fe(2), and one P(1) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Na(1) and one Fe(1) atom. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Ca(1), one Fe(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Ca(1), and one P(3) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Na(2), one P(1), and one P(3) atom. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one Na(2), one Fe(1), and one P(4) atom. In the ninth O site, O(9) is bonded in a 3-coordinate geometry to one Na(1), one Ca(1), and one P(4) atom. In the tenth O site, O(10) is bonded in a 2-coordinate geometry to one Fe(2) and one O(12) atom. The O(10)-O(12) bond length is 1.33 Å. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Na(2), one Fe(2), and one P(2) atom. In the twelfth O site, O(12) is bonded in a distorted see-saw-like geometry to one Na(3), two equivalent Na(1), and one O(10) atom.