Na4Hf2(GeO4)3 crystallizes in the trigonal R-3c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to two equivalent O(1) and four equivalent O(2) atoms. Hf(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form HfO6 octahedra that share corners with six equivalent Ge(1)O4 tetrahedra. Ge(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with four equivalent Hf(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-42°. There are two inequivalent O sites. In the first O site, O(2) is bonded to one Na(1), two equivalent Na(2), one Hf(1), and one Ge(1) atom to form a mixture of distorted corner, edge, and face-sharing ONa3HfGe trigonal bipyramids. In the second O site, O(1) is bonded in a 3-coordinate geometry to one Na(2), one Hf(1), and one Ge(1) atom.
Na4Hf2(GeO4)3 crystallizes in the trigonal R-3c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. All Na(1)-O(2) bond lengths are 2.41 Å. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to two equivalent O(1) and four equivalent O(2) atoms. Both Na(2)-O(1) bond lengths are 2.57 Å. There are two shorter (2.51 Å) and two longer (2.61 Å) Na(2)-O(2) bond lengths. Hf(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form HfO6 octahedra that share corners with six equivalent Ge(1)O4 tetrahedra. All Hf(1)-O(1) bond lengths are 2.01 Å. All Hf(1)-O(2) bond lengths are 2.11 Å. Ge(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with four equivalent Hf(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-42°. Both Ge(1)-O(1) bond lengths are 1.75 Å. Both Ge(1)-O(2) bond lengths are 1.75 Å. There are two inequivalent O sites. In the first O site, O(2) is bonded to one Na(1), two equivalent Na(2), one Hf(1), and one Ge(1) atom to form a mixture of distorted corner, edge, and face-sharing ONa3HfGe trigonal bipyramids. In the second O site, O(1) is bonded in a 3-coordinate geometry to one Na(2), one Hf(1), and one Ge(1) atom.