Na4MgY(PO4)3 crystallizes in the trigonal R3c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(4) atoms. Mg(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. Y(1) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form YO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with two equivalent Y(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-37°. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Na(2), two equivalent Na(1), one Mg(1), and one P(1) atom to form distorted face-sharing ONa3MgP trigonal bipyramids. In the second O site, O(4) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Y(1), and one P(1) atom. In the third O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Mg(1), and one P(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to one Na(1), one Y(1), and one P(1) atom.
Na4MgY(PO4)3 crystallizes in the trigonal R3c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms. The Na(1)-O(1) bond length is 2.67 Å. The Na(1)-O(2) bond length is 2.79 Å. There is one shorter (2.47 Å) and one longer (2.54 Å) Na(1)-O(3) bond length. There is one shorter (2.52 Å) and one longer (2.72 Å) Na(1)-O(4) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(4) atoms. All Na(2)-O(3) bond lengths are 2.48 Å. All Na(2)-O(4) bond lengths are 2.74 Å. Mg(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. All Mg(1)-O(1) bond lengths are 2.10 Å. All Mg(1)-O(3) bond lengths are 2.21 Å. Y(1) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form YO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. All Y(1)-O(2) bond lengths are 2.18 Å. All Y(1)-O(4) bond lengths are 2.25 Å. P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with two equivalent Y(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-37°. The P(1)-O(1) bond length is 1.54 Å. The P(1)-O(2) bond length is 1.55 Å. The P(1)-O(3) bond length is 1.56 Å. The P(1)-O(4) bond length is 1.56 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded to one Na(2), two equivalent Na(1), one Mg(1), and one P(1) atom to form distorted face-sharing ONa3MgP trigonal bipyramids. In the second O site, O(4) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Y(1), and one P(1) atom. In the third O site, O(1) is bonded in a 2-coordinate geometry to one Na(1), one Mg(1), and one P(1) atom. In the fourth O site, O(2) is bonded in a 2-coordinate geometry to one Na(1), one Y(1), and one P(1) atom.