Ba2Mn(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 7-coordinate geometry to one O(1), one O(3), one O(5), one O(7), one O(8), and two equivalent O(2) atoms. In the second Ba site, Ba(2) 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. Mn(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 MnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, 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 Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-46°. 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 Mn(1)O6 octahedra and  an edgeedge with one Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-65°. 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(2) and one P(1) atom. In the second O site, O(5) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one Mn(1), and one P(2) atom. In the third O site, O(6) is bonded in a 3-coordinate geometry to one Ba(2), one Mn(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 Mn(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 Mn(1), and one P(2) atom. In the sixth O site, O(1) is bonded in a 3-coordinate geometry to one Ba(1), one Mn(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), 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 Mn(1), and one P(1) atom.
Ba2Mn(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 7-coordinate geometry to one O(1), one O(3), one O(5), one O(7), one O(8), and two equivalent O(2) atoms. The Ba(1)-O(1) bond length is 2.76 Å. The Ba(1)-O(3) bond length is 2.74 Å. The Ba(1)-O(5) bond length is 2.79 Å. The Ba(1)-O(7) bond length is 2.77 Å. The Ba(1)-O(8) bond length is 2.81 Å. There is one shorter (2.87 Å) and one longer (2.95 Å) Ba(1)-O(2) bond length. In the second Ba site, Ba(2) 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(2)-O(2) bond length is 2.86 Å. The Ba(2)-O(3) bond length is 3.14 Å. The Ba(2)-O(5) bond length is 2.99 Å. The Ba(2)-O(6) bond length is 2.89 Å. The Ba(2)-O(7) bond length is 2.79 Å. The Ba(2)-O(8) bond length is 2.72 Å. There is one shorter (2.73 Å) and one longer (2.75 Å) Ba(2)-O(4) bond length. Mn(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 MnO6 octahedra that share corners with two equivalent P(1)O4 tetrahedra, corners with two equivalent P(2)O4 tetrahedra, and  an edgeedge with one P(2)O4 tetrahedra. The Mn(1)-O(1) bond length is 2.15 Å. The Mn(1)-O(3) bond length is 2.20 Å. The Mn(1)-O(5) bond length is 2.20 Å. The Mn(1)-O(6) bond length is 2.15 Å. The Mn(1)-O(7) bond length is 2.47 Å. The Mn(1)-O(8) bond length is 2.24 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 Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-46°. The P(1)-O(1) bond length is 1.57 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 Mn(1)O6 octahedra and  an edgeedge with one Mn(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 28-65°. The P(2)-O(5) bond length is 1.57 Å. The P(2)-O(6) bond length is 1.54 Å. The P(2)-O(7) bond length is 1.56 Å. The P(2)-O(8) bond length is 1.56 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(2) and one P(1) atom. In the second O site, O(5) is bonded in a 4-coordinate geometry to one Ba(1), one Ba(2), one Mn(1), and one P(2) atom. In the third O site, O(6) is bonded in a 3-coordinate geometry to one Ba(2), one Mn(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 Mn(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 Mn(1), and one P(2) atom. In the sixth O site, O(1) is bonded in a 3-coordinate geometry to one Ba(1), one Mn(1), and one P(1) atom. In the seventh O site, O(2) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), 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 Mn(1), and one P(1) atom.