RbK2EuV2O8 crystallizes in the trigonal P-3m1 space group. Rb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form distorted RbO12 cuboctahedra that share edges with six equivalent Rb(1)O12 cuboctahedra, edges with six equivalent V(1)O4 tetrahedra, faces with six equivalent K(1)O7 hexagonal pyramids, and faces with two equivalent Eu(1)O6 octahedra. K(1) is bonded to one O(1) and six equivalent O(2) atoms to form distorted KO7 hexagonal pyramids that share corners with six equivalent K(1)O7 hexagonal pyramids,  a cornercorner with one V(1)O4 tetrahedra, edges with three equivalent Eu(1)O6 octahedra, edges with three equivalent V(1)O4 tetrahedra, and faces with three equivalent Rb(1)O12 cuboctahedra. Eu(1) is bonded to six equivalent O(2) atoms to form EuO6 octahedra that share corners with six equivalent V(1)O4 tetrahedra, edges with six equivalent K(1)O7 hexagonal pyramids, and faces with two equivalent Rb(1)O12 cuboctahedra. V(1) is bonded to one O(1) and three equivalent O(2) atoms to form VO4 tetrahedra that share  a cornercorner with one K(1)O7 hexagonal pyramid, corners with three equivalent Eu(1)O6 octahedra, edges with three equivalent Rb(1)O12 cuboctahedra, and edges with three equivalent K(1)O7 hexagonal pyramids. The corner-sharing octahedral tilt angles are 17°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to three equivalent Rb(1), one K(1), and one V(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), two equivalent K(1), one Eu(1), and one V(1) atom.
RbK2EuV2O8 crystallizes in the trigonal P-3m1 space group. Rb(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form distorted RbO12 cuboctahedra that share edges with six equivalent Rb(1)O12 cuboctahedra, edges with six equivalent V(1)O4 tetrahedra, faces with six equivalent K(1)O7 hexagonal pyramids, and faces with two equivalent Eu(1)O6 octahedra. All Rb(1)-O(1) bond lengths are 3.54 Å. All Rb(1)-O(2) bond lengths are 3.18 Å. K(1) is bonded to one O(1) and six equivalent O(2) atoms to form distorted KO7 hexagonal pyramids that share corners with six equivalent K(1)O7 hexagonal pyramids,  a cornercorner with one V(1)O4 tetrahedra, edges with three equivalent Eu(1)O6 octahedra, edges with three equivalent V(1)O4 tetrahedra, and faces with three equivalent Rb(1)O12 cuboctahedra. The K(1)-O(1) bond length is 2.64 Å. All K(1)-O(2) bond lengths are 3.07 Å. Eu(1) is bonded to six equivalent O(2) atoms to form EuO6 octahedra that share corners with six equivalent V(1)O4 tetrahedra, edges with six equivalent K(1)O7 hexagonal pyramids, and faces with two equivalent Rb(1)O12 cuboctahedra. All Eu(1)-O(2) bond lengths are 2.33 Å. V(1) is bonded to one O(1) and three equivalent O(2) atoms to form VO4 tetrahedra that share  a cornercorner with one K(1)O7 hexagonal pyramid, corners with three equivalent Eu(1)O6 octahedra, edges with three equivalent Rb(1)O12 cuboctahedra, and edges with three equivalent K(1)O7 hexagonal pyramids. The corner-sharing octahedral tilt angles are 17°. The V(1)-O(1) bond length is 1.69 Å. All V(1)-O(2) bond lengths are 1.76 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to three equivalent Rb(1), one K(1), and one V(1) atom. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Rb(1), two equivalent K(1), one Eu(1), and one V(1) atom.