BaCo2(AsO4)2 crystallizes in the trigonal R-3 space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with six equivalent Co(1)O6 octahedra, edges with six equivalent Ba(1)O12 cuboctahedra, edges with six equivalent As(1)O4 tetrahedra, and faces with two equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. Co(1) is bonded to six equivalent O(2) atoms to form CoO6 octahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with six equivalent As(1)O4 tetrahedra, edges with three equivalent Co(1)O6 octahedra, and  a faceface with one Ba(1)O12 cuboctahedra. As(1) is bonded to one O(1) and three equivalent O(2) atoms to form AsO4 tetrahedra that share corners with six equivalent Co(1)O6 octahedra and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 53-57°. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one As(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), two equivalent Co(1), and one As(1) atom.
BaCo2(AsO4)2 crystallizes in the trigonal R-3 space group. Ba(1) is bonded to six equivalent O(1) and six equivalent O(2) atoms to form BaO12 cuboctahedra that share corners with six equivalent Co(1)O6 octahedra, edges with six equivalent Ba(1)O12 cuboctahedra, edges with six equivalent As(1)O4 tetrahedra, and faces with two equivalent Co(1)O6 octahedra. The corner-sharing octahedral tilt angles are 47°. All Ba(1)-O(1) bond lengths are 2.98 Å. All Ba(1)-O(2) bond lengths are 3.27 Å. Co(1) is bonded to six equivalent O(2) atoms to form CoO6 octahedra that share corners with three equivalent Ba(1)O12 cuboctahedra, corners with six equivalent As(1)O4 tetrahedra, edges with three equivalent Co(1)O6 octahedra, and  a faceface with one Ba(1)O12 cuboctahedra. There are three shorter (2.09 Å) and three longer (2.11 Å) Co(1)-O(2) bond lengths. As(1) is bonded to one O(1) and three equivalent O(2) atoms to form AsO4 tetrahedra that share corners with six equivalent Co(1)O6 octahedra and edges with three equivalent Ba(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 53-57°. The As(1)-O(1) bond length is 1.70 Å. All As(1)-O(2) bond lengths are 1.75 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one As(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Ba(1), two equivalent Co(1), and one As(1) atom.