Na4YNb(SiO4)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 distorted hexagonal planar geometry to three equivalent O(3) and three equivalent O(4) atoms. Y(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form YO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Nb(1) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form NbO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Y(1)O6 octahedra and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-39°. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Y(1), and one Si(1) atom. In the second O site, O(4) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Nb(1), and one Si(1) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Y(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Nb(1), and one Si(1) atom.
Na4YNb(SiO4)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 2.59 Å. The Na(1)-O(2) bond length is 2.92 Å. There is one shorter (2.39 Å) and one longer (2.65 Å) Na(1)-O(3) bond length. There is one shorter (2.53 Å) and one longer (2.81 Å) Na(1)-O(4) bond length. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to three equivalent O(3) and three equivalent O(4) atoms. All Na(2)-O(3) bond lengths are 2.60 Å. All Na(2)-O(4) bond lengths are 2.64 Å. Y(1) is bonded to three equivalent O(1) and three equivalent O(3) atoms to form YO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. All Y(1)-O(1) bond lengths are 2.15 Å. All Y(1)-O(3) bond lengths are 2.27 Å. Nb(1) is bonded to three equivalent O(2) and three equivalent O(4) atoms to form NbO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. All Nb(1)-O(2) bond lengths are 1.99 Å. All Nb(1)-O(4) bond lengths are 2.11 Å. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with two equivalent Y(1)O6 octahedra and corners with two equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 21-39°. The Si(1)-O(1) bond length is 1.60 Å. The Si(1)-O(2) bond length is 1.72 Å. The Si(1)-O(3) bond length is 1.62 Å. The Si(1)-O(4) bond length is 1.68 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Y(1), and one Si(1) atom. In the second O site, O(4) is bonded in a 5-coordinate geometry to one Na(2), two equivalent Na(1), one Nb(1), and one Si(1) atom. In the third O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Y(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Nb(1), and one Si(1) atom.