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Rb4Al2Nb35O70 crystallizes in the trigonal P-3 space group. The structure is three-dimensional. there are two inequivalent Rb sites. In the first Rb site, Rb is bonded to twelve O atoms to form distorted RbO12 cuboctahedra that share corners with six NbO6 octahedra, edges with three equivalent RbO12 cuboctahedra, edges with three equivalent NbO6 octahedra, edges with three equivalent NbO5 square pyramids, and faces with three equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 42–57°. There are a spread of Rb–O bond distances ranging from 3.11–3.27 Å. In the second Rb site, Rb is bonded to twelve O atoms to form RbO12 cuboctahedra that share corners with three equivalent NbO6 octahedra, corners with six NbO5 square pyramids, edges with three equivalent NbO5 square pyramids, faces with four NbO6 octahedra, and faces with three equivalent NbO5 square pyramids. The corner-sharing octahedral tilt angles are 43°. There are a spread of Rb–O bond distances ranging from 2.95–3.06 Å. There are eight inequivalent Nb sites. In the first Nb site, Nb is bonded to six O atoms to form distorted NbO6 octahedra that share a cornercorner with one RbO12 cuboctahedra, corners with two NbO6 octahedra, corners with three equivalent NbO5 square pyramids, a cornercorner with one AlO4 tetrahedra, an edgeedge with one RbO12 cuboctahedra, edges with two equivalent NbO6 octahedra, and a faceface with one RbO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 34–45°. There are a spread of Nb–O bond distances ranging from 1.87–2.33 Å. In the second Nb site, Nb is bonded to six O atoms to form NbO6 octahedra that share corners with three equivalent NbO6 octahedra, corners with three equivalent NbO5 square pyramids, edges with three equivalent NbO5 square pyramids, and a faceface with one RbO12 cuboctahedra. The corner-sharing octahedral tilt angles are 45°. There are three shorter (2.02 Å) and three longer (2.04 Å) Nb–O bond lengths. In the third Nb site, Nb is bonded to five O atoms to form NbO5 square pyramids that share corners with four NbO6 octahedra, corners with four equivalent NbO5 square pyramids, an edgeedge with one RbO12 cuboctahedra, and an edgeedge with one NbO6 octahedra. The corner-sharing octahedra tilt angles range from 6–53°. There are a spread of Nb–O bond distances ranging from 2.07–2.28 Å. In the fourth Nb site, Nb is bonded to five O atoms to form NbO5 square pyramids that share a cornercorner with one RbO12 cuboctahedra, corners with three equivalent NbO6 octahedra, corners with four NbO5 square pyramids, a cornercorner with one AlO4 tetrahedra, an edgeedge with one RbO12 cuboctahedra, and an edgeedge with one NbO6 octahedra. The corner-sharing octahedra tilt angles range from 43–51°. There are a spread of Nb–O bond distances ranging from 2.08–2.24 Å. In the fifth Nb site, Nb is bonded to five O atoms to form NbO5 square pyramids that share a cornercorner with one RbO12 cuboctahedra, corners with three NbO6 octahedra, corners with four NbO5 square pyramids, a cornercorner with one AlO4 tetrahedra, an edgeedge with one NbO6 octahedra, and a faceface with one RbO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 4–15°. There are a spread of Nb–O bond distances ranging from 2.05–2.35 Å. In the sixth Nb site, Nb is bonded to six O atoms to form NbO6 octahedra that share a cornercorner with one RbO12 cuboctahedra, a cornercorner with one NbO6 octahedra, corners with five NbO5 square pyramids, edges with two equivalent NbO6 octahedra, an edgeedge with one NbO5 square pyramid, and a faceface with one RbO12 cuboctahedra. The corner-sharing octahedral tilt angles are 41°. There are a spread of Nb–O bond distances ranging from 1.95–2.21 Å. In the seventh Nb site, Nb is bonded to six O atoms to form NbO6 octahedra that share corners with three equivalent NbO6 octahedra, corners with three equivalent NbO5 square pyramids, and edges with three equivalent NbO5 square pyramids. The corner-sharing octahedral tilt angles are 41°. There are three shorter (1.97 Å) and three longer (2.13 Å) Nb–O bond lengths. In the eighth Nb site, Nb is bonded to six equivalent O atoms to form NbO6 octahedra that share corners with six equivalent RbO12 cuboctahedra and corners with six equivalent NbO6 octahedra. The corner-sharing octahedral tilt angles are 34°. All Nb–O bond lengths are 2.04 Å. Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with three equivalent NbO6 octahedra and corners with six NbO5 square pyramids. The corner-sharing octahedral tilt angles are 56°. There is three shorter (1.77 Å) and one longer (1.78 Å) Al–O bond length. There are thirteen inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to one Rb and three Nb atoms. In the second O site, O is bonded in a 4-coordinate geometry to one Rb and three Nb atoms. In the third O site, O is bonded in a distorted rectangular see-saw-like geometry to one Rb and three Nb atoms. In the fourth O site, O is bonded in a distorted T-shaped geometry to one Rb and three Nb atoms. In the fifth O site, O is bonded in a distorted rectangular see-saw-like geometry to one Rb and three Nb atoms. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to one Rb and two Nb atoms. In the seventh O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Rb and two equivalent Nb atoms. In the eighth O site, O is bonded in a distorted T-shaped geometry to two Nb and one Al atom. In the ninth O site, O is bonded in a distorted trigonal planar geometry to three Nb atoms. In the tenth O site, O is bonded in a T-shaped geometry to three Nb atoms. In the eleventh O site, O is bonded in a 1-coordinate geometry to three equivalent Nb and one Al atom. In the twelfth O site, O is bonded in a distorted T-shaped geometry to three Nb atoms. In the thirteenth O site, O is bonded in a trigonal non-coplanar geometry to three equivalent Nb atoms.

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