Ba2Co(PO4)2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(5), one O(6), one O(7), one O(8), and two equivalent O(4) atoms. In the second Ba site, Ba(2) is bonded to one O(1), one O(3), one O(5), one O(7), one O(8), and two equivalent O(2) atoms to form distorted BaO7 pentagonal bipyramids that share corners with three equivalent Co(1)O6 octahedra, corners with two equivalent Ba(2)O7 pentagonal bipyramids,  a cornercorner with one P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-79°. Co(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted CoO6 octahedra that share corners with three equivalent Ba(2)O7 pentagonal bipyramids, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Ba(2)O7 pentagonal bipyramid, and  an edgeedge with one P(2)O4 tetrahedra. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Co(1)O6 octahedra and corners with four equivalent Ba(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 38-44°. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Co(1)O6 octahedra,  a cornercorner with one Ba(2)O7 pentagonal bipyramid,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Ba(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 31-59°. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(1) atom. In the second O site, O(5) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(2), one Co(1), and one P(2) atom. In the third O site, O(6) is bonded in a 3-coordinate geometry to one Ba(1), one Co(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Co(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one Co(1), and one P(2) atom. In the sixth O site, O(1) is bonded in a 3-coordinate geometry to one Ba(2), one Co(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one P(1) atom. In the eighth O site, O(3) is bonded in a 3-coordinate geometry to one Ba(1), one Ba(2), one Co(1), and one P(1) atom.
Ba2Co(PO4)2 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(2), one O(3), one O(5), one O(6), one O(7), one O(8), and two equivalent O(4) atoms. The Ba(1)-O(2) bond length is 2.85 Å. The Ba(1)-O(3) bond length is 3.20 Å. The Ba(1)-O(5) bond length is 3.03 Å. The Ba(1)-O(6) bond length is 2.84 Å. The Ba(1)-O(7) bond length is 2.76 Å. The Ba(1)-O(8) bond length is 2.69 Å. Both Ba(1)-O(4) bond lengths are 2.75 Å. In the second Ba site, Ba(2) is bonded to one O(1), one O(3), one O(5), one O(7), one O(8), and two equivalent O(2) atoms to form distorted BaO7 pentagonal bipyramids that share corners with three equivalent Co(1)O6 octahedra, corners with two equivalent Ba(2)O7 pentagonal bipyramids,  a cornercorner with one P(2)O4 tetrahedra, corners with four equivalent P(1)O4 tetrahedra,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one P(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-79°. The Ba(2)-O(1) bond length is 2.72 Å. The Ba(2)-O(3) bond length is 2.72 Å. The Ba(2)-O(5) bond length is 2.84 Å. The Ba(2)-O(7) bond length is 2.73 Å. The Ba(2)-O(8) bond length is 2.85 Å. There is one shorter (2.87 Å) and one longer (2.93 Å) Ba(2)-O(2) bond length. Co(1) is bonded to one O(1), one O(3), one O(5), one O(6), one O(7), and one O(8) atom to form distorted CoO6 octahedra that share corners with three equivalent Ba(2)O7 pentagonal bipyramids, corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra,  an edgeedge with one Ba(2)O7 pentagonal bipyramid, and  an edgeedge with one P(2)O4 tetrahedra. The Co(1)-O(1) bond length is 2.07 Å. The Co(1)-O(3) bond length is 2.10 Å. The Co(1)-O(5) bond length is 2.07 Å. The Co(1)-O(6) bond length is 2.13 Å. The Co(1)-O(7) bond length is 2.54 Å. The Co(1)-O(8) bond length is 2.10 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form PO4 tetrahedra that share corners with two equivalent Co(1)O6 octahedra and corners with four equivalent Ba(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 38-44°. The P(1)-O(1) bond length is 1.56 Å. The P(1)-O(2) bond length is 1.56 Å. The P(1)-O(3) bond length is 1.57 Å. The P(1)-O(4) bond length is 1.56 Å. In the second P site, P(2) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form PO4 tetrahedra that share corners with two equivalent Co(1)O6 octahedra,  a cornercorner with one Ba(2)O7 pentagonal bipyramid,  an edgeedge with one Co(1)O6 octahedra, and  an edgeedge with one Ba(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles range from 31-59°. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(6) bond length is 1.53 Å. The P(2)-O(7) bond length is 1.55 Å. The P(2)-O(8) bond length is 1.57 Å. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a distorted single-bond geometry to two equivalent Ba(1) and one P(1) atom. In the second O site, O(5) is bonded in a 2-coordinate geometry to one Ba(1), one Ba(2), one Co(1), and one P(2) atom. In the third O site, O(6) is bonded in a 3-coordinate geometry to one Ba(1), one Co(1), and one P(2) atom. In the fourth O site, O(7) is bonded in a distorted single-bond geometry to one Ba(1), one Ba(2), one Co(1), and one P(2) atom. In the fifth O site, O(8) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one Co(1), and one P(2) atom. In the sixth O site, O(1) is bonded in a 3-coordinate geometry to one Ba(2), one Co(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one P(1) atom. In the eighth O site, O(3) is bonded in a 3-coordinate geometry to one Ba(1), one Ba(2), one Co(1), and one P(1) atom.