RbTa(PO4)2 crystallizes in the monoclinic C2/m space group. Rb(1) is bonded in a 10-coordinate geometry to four equivalent O(2) and six equivalent O(1) atoms. Ta(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. P(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with three equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 18-31°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Rb(1), one Ta(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ta(1) and one P(1) atom.
RbTa(PO4)2 crystallizes in the monoclinic C2/m space group. Rb(1) is bonded in a 10-coordinate geometry to four equivalent O(2) and six equivalent O(1) atoms. All Rb(1)-O(2) bond lengths are 3.27 Å. There are two shorter (3.07 Å) and four longer (3.25 Å) Rb(1)-O(1) bond lengths. Ta(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with six equivalent P(1)O4 tetrahedra. Both Ta(1)-O(3) bond lengths are 1.95 Å. All Ta(1)-O(2) bond lengths are 1.99 Å. P(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form PO4 tetrahedra that share corners with three equivalent Ta(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 18-31°. The P(1)-O(1) bond length is 1.49 Å. The P(1)-O(3) bond length is 1.57 Å. Both P(1)-O(2) bond lengths are 1.57 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Rb(1) and one P(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Rb(1), one Ta(1), and one P(1) atom. In the third O site, O(3) is bonded in a bent 150 degrees geometry to one Ta(1) and one P(1) atom.