Ba6Mg7F26 crystallizes in the orthorhombic Immm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent F(5), two equivalent F(7), four equivalent F(1), and four equivalent F(2) atoms to form distorted BaF12 cuboctahedra that share corners with two equivalent Ba(1)F12 cuboctahedra,  a faceface with one Ba(1)F12 cuboctahedra, faces with two equivalent Mg(2)F6 octahedra, faces with two equivalent Mg(3)F6 octahedra, and faces with two equivalent Mg(4)F6 octahedra. In the second Ba site, Ba(2) is bonded in a 12-coordinate geometry to one F(5), one F(6), two equivalent F(2), two equivalent F(3), two equivalent F(7), and four equivalent F(1) atoms. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent F(3), two equivalent F(4), and two equivalent F(6) atoms to form a mixture of edge and corner-sharing MgF6 octahedra. The corner-sharing octahedral tilt angles range from 48-50°. In the second Mg site, Mg(2) is bonded to two equivalent F(2), two equivalent F(3), and two equivalent F(7) atoms to form MgF6 octahedra that share corners with two equivalent Mg(1)F6 octahedra, corners with two equivalent Mg(4)F6 octahedra, and faces with two equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-50°. In the third Mg site, Mg(3) is bonded to one F(4), one F(5), and four equivalent F(1) atoms to form distorted MgF6 octahedra that share  a cornercorner with one Mg(4)F6 octahedra, corners with two equivalent Mg(1)F6 octahedra, and faces with two equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-48°. In the fourth Mg site, Mg(4) is bonded to two equivalent F(5) and four equivalent F(2) atoms to form MgF6 octahedra that share corners with two equivalent Mg(3)F6 octahedra, corners with four equivalent Mg(2)F6 octahedra, and faces with four equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-2°. There are seven inequivalent F sites. In the first F site, F(2) is bonded in a linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Mg(2), and one Mg(4) atom. In the second F site, F(3) is bonded in a 2-coordinate geometry to two equivalent Ba(2), one Mg(1), and one Mg(2) atom. In the third F site, F(4) is bonded in a distorted trigonal planar geometry to one Mg(3) and two equivalent Mg(1) atoms. In the fourth F site, F(5) is bonded in a 2-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), one Mg(3), and one Mg(4) atom. In the fifth F site, F(6) is bonded in an L-shaped geometry to two equivalent Ba(2) and two equivalent Mg(1) atoms. In the sixth F site, F(7) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Mg(2) atom. In the seventh F site, F(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Mg(3) atom.
Ba6Mg7F26 crystallizes in the orthorhombic Immm space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to two equivalent F(5), two equivalent F(7), four equivalent F(1), and four equivalent F(2) atoms to form distorted BaF12 cuboctahedra that share corners with two equivalent Ba(1)F12 cuboctahedra,  a faceface with one Ba(1)F12 cuboctahedra, faces with two equivalent Mg(2)F6 octahedra, faces with two equivalent Mg(3)F6 octahedra, and faces with two equivalent Mg(4)F6 octahedra. Both Ba(1)-F(5) bond lengths are 2.93 Å. Both Ba(1)-F(7) bond lengths are 2.69 Å. All Ba(1)-F(1) bond lengths are 2.68 Å. All Ba(1)-F(2) bond lengths are 2.98 Å. In the second Ba site, Ba(2) is bonded in a 12-coordinate geometry to one F(5), one F(6), two equivalent F(2), two equivalent F(3), two equivalent F(7), and four equivalent F(1) atoms. The Ba(2)-F(5) bond length is 3.17 Å. The Ba(2)-F(6) bond length is 3.05 Å. Both Ba(2)-F(2) bond lengths are 3.22 Å. Both Ba(2)-F(3) bond lengths are 2.82 Å. Both Ba(2)-F(7) bond lengths are 2.98 Å. There are two shorter (2.61 Å) and two longer (2.78 Å) Ba(2)-F(1) bond lengths. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent F(3), two equivalent F(4), and two equivalent F(6) atoms to form a mixture of edge and corner-sharing MgF6 octahedra. The corner-sharing octahedral tilt angles range from 48-50°. Both Mg(1)-F(3) bond lengths are 1.98 Å. Both Mg(1)-F(4) bond lengths are 2.00 Å. Both Mg(1)-F(6) bond lengths are 1.96 Å. In the second Mg site, Mg(2) is bonded to two equivalent F(2), two equivalent F(3), and two equivalent F(7) atoms to form MgF6 octahedra that share corners with two equivalent Mg(1)F6 octahedra, corners with two equivalent Mg(4)F6 octahedra, and faces with two equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 2-50°. Both Mg(2)-F(2) bond lengths are 2.06 Å. Both Mg(2)-F(3) bond lengths are 1.96 Å. Both Mg(2)-F(7) bond lengths are 1.92 Å. In the third Mg site, Mg(3) is bonded to one F(4), one F(5), and four equivalent F(1) atoms to form distorted MgF6 octahedra that share  a cornercorner with one Mg(4)F6 octahedra, corners with two equivalent Mg(1)F6 octahedra, and faces with two equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-48°. The Mg(3)-F(4) bond length is 1.98 Å. The Mg(3)-F(5) bond length is 2.26 Å. All Mg(3)-F(1) bond lengths are 1.96 Å. In the fourth Mg site, Mg(4) is bonded to two equivalent F(5) and four equivalent F(2) atoms to form MgF6 octahedra that share corners with two equivalent Mg(3)F6 octahedra, corners with four equivalent Mg(2)F6 octahedra, and faces with four equivalent Ba(1)F12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-2°. Both Mg(4)-F(5) bond lengths are 1.96 Å. All Mg(4)-F(2) bond lengths are 2.00 Å. There are seven inequivalent F sites. In the first F site, F(2) is bonded in a linear geometry to two equivalent Ba(1), two equivalent Ba(2), one Mg(2), and one Mg(4) atom. In the second F site, F(3) is bonded in a 2-coordinate geometry to two equivalent Ba(2), one Mg(1), and one Mg(2) atom. In the third F site, F(4) is bonded in a distorted trigonal planar geometry to one Mg(3) and two equivalent Mg(1) atoms. In the fourth F site, F(5) is bonded in a 2-coordinate geometry to two equivalent Ba(1), two equivalent Ba(2), one Mg(3), and one Mg(4) atom. In the fifth F site, F(6) is bonded in an L-shaped geometry to two equivalent Ba(2) and two equivalent Mg(1) atoms. In the sixth F site, F(7) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Mg(2) atom. In the seventh F site, F(1) is bonded in a 4-coordinate geometry to one Ba(1), two equivalent Ba(2), and one Mg(3) atom.