MgB7 is Magnesium tetraboride-like structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to four equivalent B(1), four equivalent B(2), and four equivalent B(4) atoms. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to four equivalent B(1), four equivalent B(3), and four equivalent B(4) atoms. In the third Mg site, Mg(3) is bonded in a 2-coordinate geometry to two equivalent B(1), two equivalent B(2), two equivalent B(3), four equivalent B(6), and four equivalent B(7) atoms. There are seven inequivalent B sites. In the first B site, B(1) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one B(2), one B(3), and one B(4) atom. In the second B site, B(2) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one B(1), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. In the third B site, B(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one B(1), one B(2), one B(4), one B(5), one B(6), and one B(7) atom. In the fourth B site, B(4) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one B(1), one B(2), one B(3), one B(5), one B(6), and one B(7) atom. In the fifth B site, B(5) is bonded in a 6-coordinate geometry to one B(2), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. In the sixth B site, B(6) is bonded in a 8-coordinate geometry to two equivalent Mg(3), one B(2), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. In the seventh B site, B(7) is bonded in a 8-coordinate geometry to two equivalent Mg(3), one B(2), one B(3), one B(4), one B(5), one B(6), and one B(7) atom.
MgB7 is Magnesium tetraboride-like structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 12-coordinate geometry to four equivalent B(1), four equivalent B(2), and four equivalent B(4) atoms. All Mg(1)-B(1) bond lengths are 2.17 Å. All Mg(1)-B(2) bond lengths are 2.45 Å. All Mg(1)-B(4) bond lengths are 2.37 Å. In the second Mg site, Mg(2) is bonded in a 12-coordinate geometry to four equivalent B(1), four equivalent B(3), and four equivalent B(4) atoms. All Mg(2)-B(1) bond lengths are 2.17 Å. All Mg(2)-B(3) bond lengths are 2.45 Å. All Mg(2)-B(4) bond lengths are 2.37 Å. In the third Mg site, Mg(3) is bonded in a 2-coordinate geometry to two equivalent B(1), two equivalent B(2), two equivalent B(3), four equivalent B(6), and four equivalent B(7) atoms. Both Mg(3)-B(1) bond lengths are 2.33 Å. Both Mg(3)-B(2) bond lengths are 2.76 Å. Both Mg(3)-B(3) bond lengths are 2.76 Å. There are two shorter (2.71 Å) and two longer (2.84 Å) Mg(3)-B(6) bond lengths. There are two shorter (2.70 Å) and two longer (2.83 Å) Mg(3)-B(7) bond lengths. There are seven inequivalent B sites. In the first B site, B(1) is bonded in a 6-coordinate geometry to one Mg(1), one Mg(2), one Mg(3), one B(2), one B(3), and one B(4) atom. The B(1)-B(2) bond length is 1.74 Å. The B(1)-B(3) bond length is 1.74 Å. The B(1)-B(4) bond length is 1.79 Å. In the second B site, B(2) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(3), one B(1), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. The B(2)-B(3) bond length is 1.78 Å. The B(2)-B(4) bond length is 1.82 Å. The B(2)-B(5) bond length is 1.82 Å. The B(2)-B(6) bond length is 1.78 Å. The B(2)-B(7) bond length is 1.85 Å. In the third B site, B(3) is bonded in a 8-coordinate geometry to one Mg(2), one Mg(3), one B(1), one B(2), one B(4), one B(5), one B(6), and one B(7) atom. The B(3)-B(4) bond length is 1.82 Å. The B(3)-B(5) bond length is 1.82 Å. The B(3)-B(6) bond length is 1.85 Å. The B(3)-B(7) bond length is 1.78 Å. In the fourth B site, B(4) is bonded in a 8-coordinate geometry to one Mg(1), one Mg(2), one B(1), one B(2), one B(3), one B(5), one B(6), and one B(7) atom. The B(4)-B(5) bond length is 1.85 Å. The B(4)-B(6) bond length is 1.79 Å. The B(4)-B(7) bond length is 1.79 Å. In the fifth B site, B(5) is bonded in a 6-coordinate geometry to one B(2), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. The B(5)-B(5) bond length is 1.75 Å. The B(5)-B(6) bond length is 1.81 Å. The B(5)-B(7) bond length is 1.81 Å. In the sixth B site, B(6) is bonded in a 8-coordinate geometry to two equivalent Mg(3), one B(2), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. The B(6)-B(6) bond length is 1.80 Å. The B(6)-B(7) bond length is 1.86 Å. In the seventh B site, B(7) is bonded in a 8-coordinate geometry to two equivalent Mg(3), one B(2), one B(3), one B(4), one B(5), one B(6), and one B(7) atom. The B(7)-B(7) bond length is 1.80 Å.