Na4Zr2Si3O12 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(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form ZrO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. In the second Zr site, Zr(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form ZrO6 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 Zr(1)O6 octahedra and corners with two equivalent Zr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-40°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), two equivalent Na(1), one Zr(1), and one Si(1) atom to form a mixture of distorted corner, edge, and face-sharing ONa3ZrSi trigonal bipyramids. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), one Zr(2), and one Si(1) atom to form a mixture of distorted corner, edge, and face-sharing ONa3ZrSi trigonal bipyramids. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(1), one Zr(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Zr(1), and one Si(1) atom.
Na4Zr2Si3O12 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(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms. The Na(1)-O(3) bond length is 2.78 Å. The Na(1)-O(4) bond length is 2.59 Å. There is one shorter (2.59 Å) and one longer (2.61 Å) Na(1)-O(1) bond length. There is one shorter (2.55 Å) and one longer (2.57 Å) Na(1)-O(2) bond length. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to three equivalent O(1) and three equivalent O(2) atoms. All Na(2)-O(1) bond lengths are 2.49 Å. All Na(2)-O(2) bond lengths are 2.52 Å. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to three equivalent O(1) and three equivalent O(4) atoms to form ZrO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. All Zr(1)-O(1) bond lengths are 2.16 Å. All Zr(1)-O(4) bond lengths are 2.07 Å. In the second Zr site, Zr(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form ZrO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. All Zr(2)-O(2) bond lengths are 2.17 Å. All Zr(2)-O(3) bond lengths are 2.06 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 Zr(1)O6 octahedra and corners with two equivalent Zr(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 25-40°. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(3) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.64 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), two equivalent Na(1), one Zr(1), and one Si(1) atom to form a mixture of distorted corner, edge, and face-sharing ONa3ZrSi trigonal bipyramids. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), one Zr(2), and one Si(1) atom to form a mixture of distorted corner, edge, and face-sharing ONa3ZrSi trigonal bipyramids. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Na(1), one Zr(2), and one Si(1) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(1), one Zr(1), and one Si(1) atom.