Rb3LiErV2O8 crystallizes in the trigonal P3m1 space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(1) and six equivalent O(4) atoms to form RbO7 hexagonal pyramids that share corners with six equivalent Rb(1)O7 hexagonal pyramids,  a cornercorner with one V(1)O4 tetrahedra, edges with three equivalent Er(1)O6 octahedra, and edges with three equivalent V(2)O4 tetrahedra. In the second Rb site, Rb(2) is bonded to one O(2) and six equivalent O(3) atoms to form RbO7 hexagonal pyramids that share corners with six equivalent Rb(2)O7 hexagonal pyramids,  a cornercorner with one V(2)O4 tetrahedra, edges with three equivalent Er(1)O6 octahedra, and edges with three equivalent V(1)O4 tetrahedra. In the third Rb site, Rb(3) is bonded in a 7-coordinate geometry to one Li(1), three equivalent O(2), and three equivalent O(4) atoms. Li(1) is bonded in a 3-coordinate geometry to one Rb(3) and three equivalent O(3) atoms. Er(1) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form ErO6 octahedra that share corners with three equivalent V(1)O4 tetrahedra, corners with three equivalent V(2)O4 tetrahedra, edges with three equivalent Rb(1)O7 hexagonal pyramids, and edges with three equivalent Rb(2)O7 hexagonal pyramids. There are two inequivalent V sites. In the first V site, V(1) is bonded to one O(1) and three equivalent O(3) atoms to form VO4 tetrahedra that share  a cornercorner with one Rb(1)O7 hexagonal pyramid, corners with three equivalent Er(1)O6 octahedra, and edges with three equivalent Rb(2)O7 hexagonal pyramids. The corner-sharing octahedral tilt angles are 21°. In the second V site, V(2) is bonded to one O(2) and three equivalent O(4) atoms to form VO4 tetrahedra that share  a cornercorner with one Rb(2)O7 hexagonal pyramid, corners with three equivalent Er(1)O6 octahedra, and edges with three equivalent Rb(1)O7 hexagonal pyramids. The corner-sharing octahedral tilt angles are 19°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Rb(1) and one V(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Rb(2), three equivalent Rb(3), and one V(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Rb(2), one Li(1), one Er(1), and one V(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Rb(3), two equivalent Rb(1), one Er(1), and one V(2) atom.
Rb3LiErV2O8 crystallizes in the trigonal P3m1 space group. There are three inequivalent Rb sites. In the first Rb site, Rb(1) is bonded to one O(1) and six equivalent O(4) atoms to form RbO7 hexagonal pyramids that share corners with six equivalent Rb(1)O7 hexagonal pyramids,  a cornercorner with one V(1)O4 tetrahedra, edges with three equivalent Er(1)O6 octahedra, and edges with three equivalent V(2)O4 tetrahedra. The Rb(1)-O(1) bond length is 3.12 Å. All Rb(1)-O(4) bond lengths are 3.00 Å. In the second Rb site, Rb(2) is bonded to one O(2) and six equivalent O(3) atoms to form RbO7 hexagonal pyramids that share corners with six equivalent Rb(2)O7 hexagonal pyramids,  a cornercorner with one V(2)O4 tetrahedra, edges with three equivalent Er(1)O6 octahedra, and edges with three equivalent V(1)O4 tetrahedra. The Rb(2)-O(2) bond length is 3.11 Å. All Rb(2)-O(3) bond lengths are 3.02 Å. In the third Rb site, Rb(3) is bonded in a 7-coordinate geometry to one Li(1), three equivalent O(2), and three equivalent O(4) atoms. The Rb(3)-Li(1) bond length is 2.68 Å. All Rb(3)-O(2) bond lengths are 3.44 Å. All Rb(3)-O(4) bond lengths are 2.87 Å. Li(1) is bonded in a 3-coordinate geometry to one Rb(3) and three equivalent O(3) atoms. All Li(1)-O(3) bond lengths are 1.94 Å. Er(1) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form ErO6 octahedra that share corners with three equivalent V(1)O4 tetrahedra, corners with three equivalent V(2)O4 tetrahedra, edges with three equivalent Rb(1)O7 hexagonal pyramids, and edges with three equivalent Rb(2)O7 hexagonal pyramids. All Er(1)-O(3) bond lengths are 2.26 Å. All Er(1)-O(4) bond lengths are 2.25 Å. There are two inequivalent V sites. In the first V site, V(1) is bonded to one O(1) and three equivalent O(3) atoms to form VO4 tetrahedra that share  a cornercorner with one Rb(1)O7 hexagonal pyramid, corners with three equivalent Er(1)O6 octahedra, and edges with three equivalent Rb(2)O7 hexagonal pyramids. The corner-sharing octahedral tilt angles are 21°. The V(1)-O(1) bond length is 1.73 Å. All V(1)-O(3) bond lengths are 1.88 Å. In the second V site, V(2) is bonded to one O(2) and three equivalent O(4) atoms to form VO4 tetrahedra that share  a cornercorner with one Rb(2)O7 hexagonal pyramid, corners with three equivalent Er(1)O6 octahedra, and edges with three equivalent Rb(1)O7 hexagonal pyramids. The corner-sharing octahedral tilt angles are 19°. The V(2)-O(2) bond length is 1.69 Å. All V(2)-O(4) bond lengths are 1.77 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to one Rb(1) and one V(1) atom. In the second O site, O(2) is bonded in a distorted single-bond geometry to one Rb(2), three equivalent Rb(3), and one V(2) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to two equivalent Rb(2), one Li(1), one Er(1), and one V(1) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Rb(3), two equivalent Rb(1), one Er(1), and one V(2) atom.